Semiconductor power device having a super-junction structure

ABSTRACT

In a semiconductor power device such as a power MOSFET having a super-junction structure in each of an active cell region and a chip peripheral region, an outer end of a surface region of a second conductivity type coupled to a main junction of the second conductivity type in a surface of a drift region of a first conductivity type and having a concentration lower than that of the main junction is located in a middle region between an outer end of the main junction and an outer end of the super-junction structure in the chip peripheral region.

CROSS-REFERENCE TO RELATED APPLICATIONS

The disclosure of Japanese Patent Application No. 2010-292119 filed onDec. 28, 2010 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to a technology which is effective whenapplied to a cell peripheral layout technique or a breakdown voltageenhancement technique in a semiconductor device (or a semiconductorintegrated circuit device).

Japanese Unexamined Patent Publication No. 2007-116190 (PatentDocument 1) or US Patent Publication No. 2005-098826 (Patent Document 2)corresponding thereto discloses various structures in regard toperipheral layout around a cell region in a power MOSFET (Metal OxideSemiconductor Field Effect Transistor) having a Super-Junction structuremanufactured by a Multi-Epitaxial method or a Trench insulating filmfilling method (in-trench ion implantation method). Examples of thestructures include a P− Resurf region, a ring-like peripheral P-typedrift region formed by an in-trench ion implantation, a verticallyarranged linear peripheral P-type drift region and a divided andvertically/parallely arranged linear peripheral P-type drift region eachformed by a trench insulating film filling method, and the like.

Japanese Unexamined Patent Publication No. Sho 59 (1984)-76466 (PatentDocument 3) or U.S. Pat. No. 4,691,224 (Patent Document 4) correspondingthereto discloses a technique which arranges a plurality of FieldLimiting Rings around a main junction in a silicon-based Planarsemiconductor device and provides a Field Plate in the form of aninsulating film coupled to the field limiting rings and inwardlyextending toward the main junction of an active region, therebyimproving a breakdown voltage.

Japanese Unexamined Patent Publication No. Hei 6 (1994)-97469 (PatentDocument 5) or U.S. Pat. No. 5,804,868 (Patent Document 6) correspondingthereto discloses a technique which places field plates brought into afloating state, i.e., Floating Field Plates over, e.g., an insulatingfilm around boundary regions between the main junction of an activeregion and field limiting rings in an IGBT (Insulated Gate BipolarTransistor) so as to prevent the IGBT from being affected by externalcharge.

A paper written by Trajkovic and three others (Non-Patent Document 1)discloses a technique which provides the both ends of each of P⁺-typefield limiting rings with a shallow low-concentration P-type region (onthe active region side) and a shallow low-concentration N-type region(on the chip-edge side) in a Termination area of a power MOSFET (PowerMetal Oxide Semiconductor Field Effect Transistor), thereby preventing areduction in breakdown voltage due to external charge.

RELATED ART DOCUMENTS Patent Documents

[Patent Document 1]

-   Japanese Unexamined Patent Publication No. 2007-116190    [Patent Document 2]-   US Patent Publication No. 2005-098826    [Patent Document 3]-   Japanese Unexamined Patent Publication No. Sho 59 (1984)-76466    [Patent Document 4]-   U.S. Pat. No. 4,691,224    [Patent Document 5]-   Japanese Unexamined Patent Publication No. Hei 6 (1994)-97469    [Patent Document 6]-   U.S. Pat. No. 5,804,868

Non-Patent Document

[Non-Patent Document 1]

-   T. Trajkovic and three others, “The effect of static and dynamic    parasitic charge in the termination area of high voltage devices and    possible solutions”, pages 263-266, ISPSD' 2000, May 22-25,    Toulouse, France.

SUMMARY

In regard to a drift region in a power MOSFET or the like, it has beenan important task to avoid restrictions imposed by a related-art SiliconLimit and develop a high-breakdown-voltage FET having a lowON-resistance or the like. To achieve the task, various methods havebeen developed which introduce a super-junction structure alternatelyhaving relatively-high-concentration Slab-like N-type columns and P-typecolumns into the drift region. The methods which introduce thesuper-junction structure are roughly divided into three types ofmethods, i.e., the multi-epitaxial method, the trench insulating filmfilling method, and a trench fill method (trench filling method ortrench epitaxial filling method). Among them, the multi-epitaxial methodin which epitaxial growth and ion implantation are repeated multipletimes has high process and design flexibility and accordinglycomplicated process steps, resulting in high cost. In the trenchinsulating film filling method, after oblique ion implantation intotrenches is performed, the trenches are filled with a CVD (ChemicalVapor Deposition) insulating film. The trench insulating film fillingmethod is simpler in terms of process, but is disadvantageous in termsof area due to the area of the trenches.

By contrast, the trench fill method has relatively low process anddesign flexibility due to constraints on growth conditions for fillingepitaxial growth, but has the advantage of simple process steps. In viewof this, the present inventors have studied problems associated with adevice structure and mass production of a power MOSFET or the like inrelation to a high breakdown voltage and a low ON-resistance to beachieved by the trench fill method or the like and found the followingproblem. That is, in the super-junction structure, the concentration ofa main body cell portion (active region) is relatively high, andtherefore it is difficult to ensure a breakdown voltage equal to orhigher than that of the cell portion for a peripheral portion(peripheral region or junction termination area) using a related-artedge termination structure (Junction Edge Termination Structure) or arelated-art Resurf (Reduced Surface Field) Structure. Specifically, theproblem is such that, in an outer peripheral corner portion of a chip,due to electric field concentration, variations in breakdown voltagebecome sensitive to charge unbalance in the super-junction structure.

The present invention has been achieved in order to solve such aproblem.

An object of the present invention is to provide a semiconductor devicesuch as a solid-state active element having a high breakdown voltage anda low ON-resistance.

The above and other objects and novel features of the present inventionwill become apparent from a statement in the present specification andthe accompanying drawings.

The following is a brief description of the outline of a representativeembodiment of the invention disclosed in the present application.

That is, according to an aspect of the present invention, in asemiconductor power device such as a power MOSFET having asuper-junction structure in each of an active cell region and a chipperipheral region, an outer end of a surface resurf region of a secondconductivity type coupled to a main junction (impurity regionsurrounding the active cell region and integrated with a channel region)of the second conductivity type in a surface of a drift region of afirst conductivity type and having a concentration lower than that ofthe main junction is located in a middle region between an outer end ofthe main junction and an outer end of the super-junction structure inthe chip peripheral region.

The following is a brief description of an effect obtained according tothe representative embodiment of the invention disclosed in the presentapplication.

That is, in a semiconductor power device such as a power MOSFET having asuper-junction structure in each of an active cell region and a chipperipheral region, an outer end of a surface resurf region of a secondconductivity type coupled to a main junction (impurity regionsurrounding the active cell region and integrated with a channel region)of the second conductivity type in a surface of a drift region of afirst conductivity type and having a concentration lower than that ofthe main junction is located in a middle region between an outer end ofthe main junction and an outer end of the super-junction structure inthe chip peripheral region to allow a position where an electric fieldis concentrated to be located away from the outer end of thesuper-junction structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an entire chip (mainly of a surface regionthereof) of a power MOSFET having a super-junction structure as anexample of a semiconductor device of a first embodiment (peripheral 3Dsuper-junction and half-range P− resurf layer) of a first part of thepresent invention;

FIG. 2 is a top view of the entire chip (mainly of an impurity dopedstructure thereof or the like) of the power MOSFET having thesuper-junction structure as the example of the semiconductor device ofthe first embodiment of the first part of the present invention;

FIG. 3 is a top view (closer to a real equivalent) of a local portion ofthe chip corresponding to a cut-away region R1 of the chip cornerportion of FIG. 1;

FIG. 4 is a top view (schematic diagram for illustration) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion of FIG. 1;

FIG. 5 is a cross-sectional view of a local portion of the chipcorresponding to the X-X′ cross section of FIG. 4;

FIG. 6 is a cross-sectional view of a local portion of the chipcorresponding to the Y-Y′ cross section of FIG. 4;

FIG. 7 is a cross-sectional view of a local portion of the chip(corresponding to two active cells) corresponding to the A-A′ crosssection of a cut-away region R2 of the active cell portion of FIG. 1;

FIG. 8 is a wafer cross-sectional view of a device portion shown in FIG.5 for illustrating a wafer process (step of forming trenches)corresponding to the semiconductor device of the first embodiment of thefirst part of the present invention;

FIG. 9 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of removing a hard maskfor forming the trenches) corresponding to the semiconductor device ofthe first embodiment of the first part of the present invention;

FIG. 10 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of filling the trencheswith a P-type epitaxial layer) corresponding to the semiconductor deviceof the first embodiment of the first part of the present invention;

FIG. 11 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (CMP step) corresponding tothe semiconductor device of the first embodiment of the first part ofthe present invention;

FIG. 12 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of introducing a P⁻-typesurface resurf region) corresponding to the semiconductor device of thefirst embodiment of the first part of the present invention;

FIG. 13 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of patterning a fieldoxide film) corresponding to the semiconductor device of the firstembodiment of the first part of the present invention;

FIG. 14 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of introducing a P bodyregion) corresponding to the semiconductor device of the firstembodiment of the first part of the present invention;

FIG. 15 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of forming a gateinsulating film) corresponding to the semiconductor device of the firstembodiment of the first part of the present invention;

FIG. 16 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of forming a gatepolysilicon film) corresponding to the semiconductor device of the firstembodiment of the first part of the present invention;

FIG. 17 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of patterning the gatepolysilicon film into gate electrodes) corresponding to thesemiconductor device of the first embodiment of the first part of thepresent invention;

FIG. 18 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of forming sourceregions) corresponding to the semiconductor device of the firstembodiment of the first part of the present invention;

FIG. 19 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of forming an interlayerinsulating film) corresponding to the semiconductor device of the firstembodiment of the first part of the present invention;

FIG. 20 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of forming contactholes) corresponding to the semiconductor device of the first embodimentof the first part of the present invention;

FIG. 21 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of extending the contactholes and introducing body contact regions) corresponding to thesemiconductor device of the first embodiment of the first part of thepresent invention;

FIG. 22 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of forming analuminum-based conductive film) corresponding to the semiconductordevice of the first embodiment of the first part of the presentinvention;

FIG. 23 is a top view (closer to a real equivalent) of a local portionof a chip corresponding to the cut-away region R1 of the chip cornerportion of FIG. 1 of a power MOSFET having a super-junction structure asan example of a semiconductor device of a second embodiment (peripheral3D super-junction, half-range P− resurf layer, and floating fieldplates) of the present invention;

FIG. 24 is a top view (schematic diagram for illustration) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion shown in FIG. 23;

FIG. 25 is a cross-sectional view of a local portion of the chipcorresponding to the X-X′ cross section of FIG. 24;

FIG. 26 is a cross-sectional view of a local portion of the chipcorresponding to the Y-Y′ cross section of FIG. 24;

FIG. 27 is a wafer cross-sectional view (corresponding to FIG. 16 of thefirst embodiment of the first part) of the device portion shown in FIG.25 for illustrating a wafer process (step of forming a gate polysiliconfilm) corresponding to the semiconductor device of the second embodimentof the present invention;

FIG. 28 is a wafer cross-sectional view (corresponding to FIG. 17 of thefirst embodiment of the first part) of the device portion shown in FIG.25 for illustrating the wafer process (step of patterning the gatepolysilicon film into gate electrodes) corresponding to thesemiconductor device of the second embodiment of the present invention;

FIG. 29 is a wafer cross-sectional view (corresponding to FIG. 18 of thefirst embodiment of the first part) of the device portion shown in FIG.25 for illustrating the wafer process (step of forming source regions)corresponding to the semiconductor device of the second embodiment ofthe present invention;

FIG. 30 is a wafer cross-sectional view (corresponding to FIG. 19 of thefirst embodiment of the first part) of the device portion shown in FIG.25 for illustrating the wafer process (step of forming an interlayerinsulating film) corresponding to the semiconductor device of the secondembodiment of the present invention;

FIG. 31 is a wafer cross-sectional view (corresponding to FIG. 20 of thefirst embodiment of the first part) of the device portion shown in FIG.25 for illustrating the wafer process (step of forming contact holes)corresponding to the semiconductor device of the second embodiment ofthe present invention;

FIG. 32 is a wafer cross-sectional view (corresponding to FIG. 21 of thefirst embodiment of the first part) of the device portion shown in FIG.25 for illustrating the wafer process (step of extending the contactholes and introducing body contact regions) corresponding to thesemiconductor device of the second embodiment of the present invention;

FIG. 33 is a wafer cross-sectional view (corresponding to FIG. 22 of thefirst embodiment of the first part) of the device portion shown in FIG.25 for illustrating the wafer process (step of forming an aluminum-basedconductive film) corresponding to the semiconductor device of the secondembodiment of the present invention;

FIG. 34 is a top view (closer to a real equivalent) of a local portionof the chip which is the cut-away region R1 of the chip corner portioncorresponding to FIG. 3 or 23 for illustrating a variation (asymmetricalstandard arrangement) of individual components (column layout) in thesemiconductor device of each of the first and second embodiments of thefirst part of the present invention;

FIG. 35 is a top view (closer to the real equivalent) of the localportion of the chip which is the cut-away region R1 of the chip cornerportion corresponding to FIG. 3 or 23 for illustrating a variation(asymmetrical trimmed arrangement) of the individual components (columnlayout) in the semiconductor device of each of the first and secondembodiments of the first part of the present invention;

FIG. 36 is a top view (closer to the real equivalent) of the localportion of the chip which is the cut-away region R1 of the chip cornerportion corresponding to FIG. 3 or 23 for illustrating a variation(symmetrical L-shaped arrangement) of the individual components (columnlayout) in the semiconductor device of each of the first and secondembodiments of the first part of the present invention;

FIG. 37 is a top view (closer to the real equivalent) of the localportion of the chip which is the cut-away region R1 of the chip cornerportion corresponding to FIG. 3 or 23 showing a combination of theasymmetrical standard column layout of FIG. 34 and a rectangular P⁻-typesurface resurf region;

FIG. 38 is a top view (closer to the real equivalent) of the localportion of the chip which is the cut-away region R1 of the chip cornerportion corresponding to FIG. 3 or 23 showing a combination of theasymmetrical trimmed column layout of FIG. 35 and the rectangularP⁻-type surface resurf region;

FIG. 39 is a top view (closer to the real equivalent) of the localportion of the chip which is the cut-away region R1 of the chip cornerportion corresponding to FIG. 3 or 23 showing a combination of thesymmetrical L-shaped column layout of FIG. 36 and the rectangularP⁻-type surface resurf region;

FIG. 40 is a top view (closer to the real equivalent) of the localportion of the chip which is the cut-away region R1 of the chip cornerportion corresponding to FIG. 3 or 23 for illustrating a variation(right-angle bent corner portion arrangement) of the individualcomponents (layout of floating field plates) in the semiconductor deviceof the second embodiment of the present invention;

FIG. 41 is a top view (closer to the real equivalent) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion corresponding to FIG. 3 or 23 for illustrating avariation (roundly curved corner portion arrangement) of the individualcomponents (layout of floating field plates) in the semiconductor deviceof the second embodiment of the present invention;

FIG. 42 is a data plot diagram showing the charge balance ratiodependence of a source/drain breakdown voltage in each of thesemiconductor devices (power MOSFETs each having the super-junctionstructure and a half-width P⁻-type surface resurf region) of each of thefirst and second embodiments of the first part of the present inventionand a semiconductor device (power MOSFET having a super-junctionstructure and a full-width P⁻-type surface resurf region) of acomparative example;

FIG. 43 is an illustrative view showing a relationship between anelectric field intensity distribution and a peripheral charge amount ina vertical direction (thickness direction of the chip) at the middle ofa P column or the like in a peripheral portion of the chip;

FIG. 44 is an illustrative view showing a relationship between anelectric field intensity distribution and a peripheral charge amount ina middle portion of a surface region of the P column or the like in theperipheral portion of the chip;

FIG. 45 is an illustrative view for illustrating the principle of animprovement in breakdown voltage resulting from the use of thefull-width P⁻-type surface resurf region;

FIG. 46 is a perspective view of a package of a power MOSFET having asuper-junction structure or the like as a semiconductor device of eachof embodiments of a second part of the present invention;

FIG. 47 is a main-portion top view of the package of FIG. 46 from whicha mold resin has been removed;

FIG. 48 is a cross-sectional view of the package (in a state molded withthe mold resin) corresponding to the B-B′ cross section of FIG. 47;

FIG. 49 is a top view of the entire chip (mainly of a surface regionthereof) of a power MOSFET having a super-junction structure as anexample of the semiconductor device according to the first embodiment ofthe second part of the present invention;

FIG. 50 is a top view of the entire chip (mainly of an impurity dopedstructure thereof or the like) of the power MOSFET having thesuper-junction structure as the example of the semiconductor deviceaccording to the first embodiment of the second part of the presentinvention;

FIG. 51 is a top view of a local portion of the chip corresponding to acut-away region R1 of the chip corner portion of FIG. 49;

FIG. 52 is a cross-sectional view of a local portion of the chipcorresponding to the X-X′ cross section of FIG. 51;

FIG. 53 is a cross-sectional view of a local portion of the chipcorresponding to the Y-Y′ cross section of FIG. 51;

FIG. 54 is a device schematic cross-sectional view showing a positionalrelationship between the floating field plates and the P column regionsof FIG. 51;

FIG. 55 is a cross-sectional view of a local portion of the chip(corresponding to two active cells) corresponding to the A-A′ crosssection of a cut-away region R2 of the active cell portion of FIG. 49;

FIG. 56 is a wafer cross-sectional view of a device portion shown inFIG. 52 for illustrating a wafer process (step of forming trenches)corresponding to the semiconductor device of the first embodiment of thesecond part of the present invention;

FIG. 57 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of removing a hard maskfor forming the trenches) corresponding to the semiconductor device ofthe first embodiment of the second part of the present invention;

FIG. 58 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of filling the trencheswith a P-type epitaxial layer) corresponding to the semiconductor deviceof the first embodiment of the second part of the present invention;

FIG. 59 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (CMP step) corresponding tothe semiconductor device of the first embodiment of the second part ofthe present invention;

FIG. 60 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of introducing aP⁻-type surface resurf region) corresponding to the semiconductor deviceof the first embodiment of the second part of the present invention;

FIG. 61 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of patterning a fieldoxide film) corresponding to the semiconductor device of the firstembodiment of the second part of the present invention;

FIG. 62 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of introducing a P bodyregion) corresponding to the semiconductor device of the firstembodiment of the second part of the present invention;

FIG. 63 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of forming a gateinsulating film) corresponding to the semiconductor device of the firstembodiment of the second part of the present invention;

FIG. 64 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of forming a gatepolysilicon film) corresponding to the semiconductor device of the firstembodiment of the second part of the present invention;

FIG. 65 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of patterning the gatepolysilicon film into gate electrodes) corresponding to thesemiconductor device of the first embodiment of the second part of thepresent invention;

FIG. 66 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of forming sourceregions) corresponding to the semiconductor device of the firstembodiment of the second part of the present invention;

FIG. 67 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of forming aninterlayer insulating film) corresponding to the semiconductor device ofthe first embodiment of the second part of the present invention;

FIG. 68 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of forming contactholes) corresponding to the semiconductor device of the first embodimentof the second part of the present invention;

FIG. 69 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of extending thecontact holes and introducing body contact regions) corresponding to thesemiconductor device of the first embodiment of the second part of thepresent invention;

FIG. 70 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of forming analuminum-based conductive film) corresponding to the semiconductordevice of the first embodiment of the second part of the presentinvention;

FIG. 71 is a top view of a local portion of a chip of a power MOSFEThaving a super-junction structure as an example of the semiconductordevice of the second embodiment of the second part of the presentinvention corresponding to the cut-away region R1 of the chip cornerportion of FIG. 49;

FIG. 72 is a cross-sectional view of a local portion of the chipcorresponding to the X-X′ cross section of FIG. 71;

FIG. 73 is a cross-sectional view of a local portion of the chipcorresponding to the Y-Y′ cross section of FIG. 71;

FIG. 74 is a device schematic cross-sectional view for illustrating arelationship between the N ring regions and P column regions of FIGS. 72and 73;

FIG. 75 is a wafer cross-sectional view of a device portion shown inFIG. 72 for illustrating a wafer process (step of introducing the N ringregions) corresponding to the semiconductor device of the secondembodiment of the second part of the present invention;

FIG. 76 is a wafer cross-sectional view of the device portion shown inFIG. 72 for illustrating the wafer process (step of introducing aP⁻-type surface resurf region) corresponding to the semiconductor deviceof the second embodiment of the second part of the present invention;

FIG. 77 is a top view of a local portion of a chip of a power MOSFEThaving a super-junction structure as an example of the semiconductordevice of the third embodiment of the second part of the presentinvention corresponding to the cut-away region R1 of the chip cornerportion of FIG. 49;

FIG. 78 is a cross-sectional view of a local portion of the chipcorresponding to the X-X′ cross section of FIG. 77;

FIG. 79 is a cross-sectional view of a local portion of the chipcorresponding to the Y-Y′ cross section of FIG. 77;

FIG. 80 is a device schematic cross-sectional view for illustrating arelationship between the N ring regions (P ring regions) and P columnregions of FIGS. 78 and 79;

FIG. 81 is a wafer cross-sectional view of a device portion shown inFIG. 78 for illustrating a wafer process (step of introducing the P ringregions) corresponding to the semiconductor device of the thirdembodiment of the second part of the present invention;

FIG. 82 is a wafer cross-sectional view of the device portion shown inFIG. 78 for illustrating the wafer process (step of introducing aP⁻-type surface resurf region) corresponding to the semiconductor deviceof the third embodiment of the second part of the present invention;

FIG. 83 is a top view (closer to a real equivalent) of the local portionof the chip corresponding to the cut-away region R1 of the chip cornerportion of FIG. 50 for illustrating a variation (asymmetrical standardarrangement) of individual components (column layout) in thesemiconductor device of each of the first to third embodiments of thesecond part of the present invention;

FIG. 84 is a top view (closer to the real equivalent) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion of FIG. 50 for illustrating a variation (asymmetricaltrimmed arrangement) of the individual components (column layout) in thesemiconductor device of each of the first to third embodiments of thesecond part of the present invention;

FIG. 85 is a top view (closer to the real equivalent) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion of FIG. 50 for illustrating a variation (symmetricalL-shaped arrangement) of the individual components (column layout) inthe semiconductor device of each of the first to third embodiments ofthe second part of the present invention;

FIG. 86 is a top view (closer to the real equivalent) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion of FIG. 50 for illustrating a variation (right-angle bentcorner portion arrangement) of the individual components (layout offloating field plates) in the semiconductor device of each of the firstto third embodiments of the second part of the present invention;

FIG. 87 is a top view (closer to the real equivalent) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion of FIG. 50 for illustrating a variation (roundly curvedcorner portion arrangement) of the individual components (layout offloating field plates) in the semiconductor device of each of the firstto third embodiments of the second part of the present invention;

FIG. 88 is a top view (closer to the real equivalent) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion of FIG. 50 for illustrating a variation (right-angle bentcorner portion arrangement) of the individual components (N ringregions) in the semiconductor device of each of the first to thirdembodiments of the second part of the present invention;

FIG. 89 is a top view (closer to the real equivalent) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion of FIG. 50 for illustrating a variation (roundly curvedcorner portion arrangement) of the individual components (N ringregions) in the semiconductor device of each of the first to thirdembodiments of the second part of the present invention;

FIG. 90 is a device schematic cross-sectional view showing a positionalrelationship between the floating field plates and P column regions eachshown in FIG. 52 or 70 or the like for illustrating a variation(stepped-insulating-film-type FFPs) of the individual components(floating field plates) in the semiconductor device of each of the firstto third embodiments of the second part of the present invention;

FIG. 91 is a (first) schematic top view of the chip for illustrating astructure of the semiconductor device of each of the first to thirdembodiments of the second part of the present invention;

FIG. 92 is a (second) schematic top view of the chip for illustratingthe structure of the semiconductor device of each of the first to thirdembodiments of the second part of the present invention;

FIG. 93 is a data plot diagram for illustrating the effect of theshifted FFPs of the first embodiment of the second part of the presentinvention;

FIG. 94 is a data plot diagram for illustrating the effect of the N ringregions of the second embodiment of the second part of the presentinvention;

FIG. 95 is a top view of a cut-away region R1 of a chip corner portionfor illustrating a charge-balanced-type 2D peripheral resurf structurein a semiconductor device of a first embodiment of a third part of thepresent invention;

FIG. 96 is a schematic top view of the chip corner portion correspondingto FIG. 95;

FIG. 97 is a locally enlarged view (for easier understanding of a chargebalancing treatment, the width of each of N columns is reduced toprovide an equal area when charge is balanced) corresponding to apartially cut-away region R3 of the corner portion of FIG. 96 subjectedto the charge balancing treatment;

FIG. 98 is a top view of the cut-away region R1 of the chip cornerportion for illustrating a charge-balanced-type 3D peripheral resurfstructure in a semiconductor device of a second embodiment of the thirdpart of the present invention;

FIG. 99 is a schematic top view of the chip corner portion correspondingto FIG. 98;

FIG. 100 is, a locally enlarged view (for easier understanding of thecharge balancing treatment, the width of each of the N columns isreduced to provide an equal area when charge is balanced) correspondingto the partially cut-away region R3 of the corner portion of FIG. 99subjected to the charge balancing treatment;

FIG. 101 is a schematic top view of a chip corner portion forillustrating a first variation (3D peripheral resurf structure andhalf-width surface resurf layer) of the second embodiment of the thirdpart of the present invention;

FIG. 102 is a top view of the cut-away region R1 of a chip cornerportion for illustrating a charge-balanced-type 2D peripheral resurfstructure in a second variation (trimming of a super-junction cornerportion) of the first embodiment of the third part of the presentinvention;

FIG. 103 is a top view of the cut-away region R1 of a chip cornerportion for illustrating a charge-balanced-type 3D peripheral resurfstructure in a second variation (trimming of the super-junction cornerportion) of the second embodiment of the third part of the presentinvention;

FIG. 104 is a schematic top view of a chip corner portion forillustrating a third variation (combination with floating field plates)of the first embodiment of the third part of the present invention;

FIG. 105 is a schematic top view of a chip corner portion forillustrating a third variation (combination with floating field plates)of the second embodiment of the third part of the present invention;

FIG. 106 is a schematic top view of a chip corner portion forillustrating a fourth variation (combination with N rings or P rings) ofthe first embodiment of the third part of the present invention;

FIG. 107 is a data plot diagram (including the result of simulation in acell portion) showing a relationship between charge balance andbreakdown voltage in a non-charge-balanced-type 2D peripheral resurfstructure;

FIG. 108 is a data plot diagram (including the result of simulation in acell portion) showing a relationship between charge balance andbreakdown voltage in a non-charge-balanced-type 3D peripheral resurfstructure; and

FIG. 109 is a data plot diagram (including the result of simulation in acell portion) showing a relationship between charge balance andbreakdown voltage in each of various 2D peripheral resurf structures.

DETAILED DESCRIPTION Outline of Embodiments

First, a description will be given to the outline of representativeembodiments (mainly related to a first part) of the invention disclosedin the present application.

1. A semiconductor device includes: (a) a semiconductor chip having afirst main surface provided with a source electrode of a power MOSFETand a second main surface provided with a drain electrode of the powerMOSFET; (b) a drift region of a first conductivity type provided insubstantially the entire first main surface of the semiconductor chip;(c) a substantially rectangular active cell region providedsubstantially at a middle portion of the first main surface, peripheralside regions provided outside the active cell region along individualsides of the active cell region, and peripheral corner regions providedoutside individual corner portions of the active cell region; (d) afirst super-junction structure having a first orientation and providedin substantially the entire surface of the cell region and in the driftregion; (e) second and third super-junction structures each havingsubstantially the same width and orientation as those of the firstsuper-junction structure and provided in the drift region of each of theperipheral side regions on both sides of the active cell region in adirection of the first orientation of the first super-junction structureso as to be coupled to the first super-junction structure; (f) fourthand fifth super-junction structures each having an orientationsubstantially orthogonal to that of the first super-junction structureand provided in the drift region of each of the peripheral side regionson both sides of the active cell region in a direction orthogonal to thefirst orientation of the first super-junction structure; (g) a mainjunction region of a second conductivity type which is an outer endportion of the active cell region and provided in a surface of the driftregion so as to surround the active cell region; and (h) a surfaceresurf region of the second conductivity type provided in the surface ofthe drift region so as to be coupled to an outer end of the mainjunction region and surround the main junction region. In thesemiconductor device, an outer end of the surface resurf region islocated in a middle region between the outer end of the main junctionregion and an outer end of a peripheral super-junction region formed ofthe second to fifth super-junction structures.

2. In the semiconductor device according to article 1, the outer end ofthe surface resurf region is located substantially at a middle betweenthe outer end of the main junction region and the outer end of theperipheral super-junction region formed of the second to fifthsuper-junction structures.

3. In the semiconductor device according to article 1 or 2, the first tofifth super-junction structures are formed by a trench epitaxial fillingmethod.

4. In the semiconductor device according to any one of articles 1 to 3,over the peripheral super-junction region formed of the second to fifthsuper-junction structures, a plurality of floating field platescircularly extending over the region are provided.

5. In the semiconductor device according to article 4, each of thefloating field plates shows a rectangular frame shape having cornerportions each bent at a right angle.

6. In the semiconductor device according to article 4, each of thefloating field plates shows a rectangular frame shape having cornerportions each roundly curved.

7. In the semiconductor device according to any one of articles 1 to 6,each of the peripheral corner regions is provided with a corner-portionsuper-junction structure which is substantially line-symmetrical withrespect to a diagonal line of the semiconductor chip extending throughthe corner-portion super-junction structure, and has a portion thereofproximate to the fourth super-junction structure with respect to thediagonal line and having substantially the same width and orientation asthose of the fourth super-junction structure and a portion thereofproximate to the second super-junction structure with respect to thediagonal line and having substantially the same width and orientation asthose of the second super-junction structure.

8. In the semiconductor device according to any one of articles 1 to 6,each of the peripheral corner regions is provided with a corner-portionsuper-junction structure having substantially the same width andorientation as those of the fourth super-junction structure.

9. In the semiconductor device according to article 8, thecorner-portion super-junction structure has a trimmed outer portion.

10. A semiconductor device includes: (a) a semiconductor chip having afirst main surface provided with a source electrode of a power MOSFETand a second main surface provided with a drain electrode of the powerMOSFET; (b) a drift region of a first conductivity type provided insubstantially the entire first main surface of the semiconductor chip;(c) a substantially rectangular active cell region providedsubstantially at a middle portion of the first main surface, peripheralside regions provided outside the active cell region along individualsides of the active cell region, and peripheral corner regions providedoutside individual corner portions of the active cell region; (d) afirst super-junction structure having a first orientation and providedin substantially the entire surface of the cell region and in the driftregion; (e) second and third super-junction structures each havingsubstantially the same width and orientation as those of the firstsuper-junction structure and provided in the drift region of each of theperipheral side regions on both sides of the active cell region in adirection of the first orientation of the first super-junction structureso as to be coupled to the first super-junction structure; (f) fourthand fifth super-junction structures each having an orientationsubstantially orthogonal to that of the first super-junction structureand provided in the drift region of each of the peripheral side regionson both sides of the active cell region in a direction orthogonal to thefirst orientation of the first super-junction structure; (g) a mainjunction region of a second conductivity type which is an outer endportion of the active cell region and provided in a surface of the driftregion so as to surround the active cell region; (h) a surface resurfregion of the second conductivity type provided in the surface of thedrift region so as to be coupled to an outer end of the main junctionregion and surround the main junction region; and (i) a corner-portionsuper-junction structure provided in each of the peripheral cornerregions, substantially line-symmetrical with respect to a diagonal lineof the semiconductor chip extending through the corner-portionsuper-junction structure, and having portion thereof proximate to thefourth super-junction structure with respect to the diagonal line andhaving substantially the same width and orientation as those of thefourth super-junction structure and a portion thereof proximate to thesecond super-junction structure with respect to the diagonal line andhaving substantially the same width and orientation as those of thesecond super-junction structure.

11. In the semiconductor device according to article 10, an outer end ofthe surface resurf region is located in a middle region between theouter end of the main junction region and an outer end of a peripheralsuper-junction region formed of the second to fifth super-junctionstructures.

12. In the semiconductor device according to article 10 or 11, the outerend of the surface resurf region is located substantially at a middlebetween the outer end of the main junction region and the outer end ofthe peripheral super-junction region formed of the second to fifthsuper-junction structures.

13. In the semiconductor device according to any one of articles 10 to12, the first to fifth super-junction structures are formed by a trenchepitaxial filling method.

14. In the semiconductor device according to any one of articles 10 to13, over the peripheral super-junction region formed of the second tofifth super-junction structures, a plurality of floating field platescircularly extending over the region are provided.

15. A semiconductor device includes: (a) a semiconductor chip having afirst main surface provided with a source electrode of a power MOSFETand a second main surface provided with a drain electrode of the powerMOSFET; (b) a drift region of a first conductivity type provided insubstantially the entire first main surface of the semiconductor chip;(c) a substantially rectangular active cell region providedsubstantially at a middle portion of the first main surface, peripheralside regions provided outside the active cell region along individualsides of the active cell region, and peripheral corner regions providedoutside individual corner portions of the active cell region; (d) afirst super-junction structure having a first orientation and providedin substantially the entire surface of the cell region and in the driftregion; (e) second and third super-junction structures each havingsubstantially the same width and orientation as those of the firstsuper-junction structure and provided in the drift region of each of theperipheral side regions on both sides of the active cell region in adirection of the first orientation of the first super-junction structureso as to be coupled to the first super-junction structure; (f) fourthand fifth super-junction structures each having an orientationsubstantially orthogonal to that of the first super-junction structureand provided in the drift region of each of the peripheral side regionson both sides of the active cell region in a direction orthogonal to thefirst orientation of the first super-junction structure; (g) a mainjunction region of a second conductivity type which is an outer endportion of the active cell region and provided in a surface of the driftregion so as to surround the active cell region; (h) a surface resurfregion of the second conductivity type provided in the surface of thedrift region so as to be coupled to an outer end of the main junctionregion and surround the main junction region; and (i) a corner-portionsuper-junction structure provided in each of the peripheral cornerregions, having substantially the same width and orientation as those ofthe fourth super-junction structure, and a trimmed outer portion.

16. In the semiconductor device according to article 15, an outer end ofthe surface resurf region is located in a middle region between theouter end of the main junction region and an outer end of a peripheralsuper-junction region formed of the second to fifth super-junctionstructures.

17. In the semiconductor device according to article 15, the outer endof the surface resurf region is located substantially at a middlebetween the outer end of the main junction region and the outer end ofthe peripheral super-junction region formed of the second to fifthsuper-junction structures.

18. In the semiconductor device according to any one of articles 15 to17, the first to fifth super-junction structures are formed by a trenchepitaxial filling method.

19. In the semiconductor device according to any one of articles 15 to18, over the peripheral super-junction region formed of the second tofifth super-junction structures, a plurality of floating field platescircularly extending over the region are provided.

Next, a description will be given to the outline of other embodiments(mainly related to a second part) of the invention disclosed in thepresent application.

1. A semiconductor device includes: (a) a semiconductor chip having afirst main surface provided with a source electrode of a power MOSFETand a second main surface provided with a drain electrode of the powerMOSFET; (b) a drift region of a first conductivity type provided insubstantially the entire first main surface of the semiconductor chip;(c) a substantially rectangular active cell region providedsubstantially at a middle portion of the first main surface, peripheralside regions provided outside the active cell region along individualsides of the active cell region, and peripheral corner regions providedoutside individual corner portions of the active cell region; (d) afirst super-junction structure having a first orientation and providedin substantially the entire surface of the cell region and in the driftregion; (e) second and third super-junction structures each having asecond orientation orthogonal to that of the first super-junctionstructure provided in the drift region of each of the peripheral sideregions on both sides of the active cell region in a direction of thefirst orientation of the first super-junction structure; (f) fourth andfifth super-junction structures each having an orientation substantiallythe same as that of the first super-junction structure and provided inthe drift region of each of the peripheral side regions on both sides ofthe active cell region in a direction orthogonal to the firstorientation of the first super-junction structure; (g) a main junctionregion of a second conductivity type which is an outer end portion ofthe active cell region and provided in a surface of the drift region soas to surround the active cell region; (h) a plurality of floating fieldplates provided over the first main surface via an insulating film andoutside the main junction region so as to surround the active cellregion; and (i) a resin molded body covering substantially the entirefirst main surface of the semiconductor chip. In the semiconductordevice, each of the floating field plates widthwise extends in a rangecovering an outer end portion of a column circular region of the secondconductivity type which is proximate to the floating field plate,extending over a middle line of the column circular region of the secondconductivity type, and not extending over a vicinity of an inner endthereof closer to the active cell region.

2. The semiconductor device according to article 1 further includes: (j)a surface resurf region of the second conductivity type provided in thesurface of the drift region so as to be coupled to an outer end of themain junction region and surround the main junction region.

3. In the semiconductor device according to article 1 or 2, the floatingfield plates are provided for each of the column circular regions of thesecond conductivity type.

4. In the semiconductor device according to any one of articles 1 to 3,each of the floating field plates shows a rectangular frame shape havingcorner portions each bent at a right angle.

5. In the semiconductor device according to any one of articles 1 to 3,each of the floating field plates shows a rectangular frame shape havingcorner portions each roundly curved.

6. The semiconductor device according to any one of articles 1 to 5further includes: (k) a ring region of the first conductivity typeprovided in the surface of the drift region and outside the mainjunction region so as to surround the active cell region along the innerend of the column circular region of the second conductivity type whichis proximate to the ring region of the first conductivity type.

7. In the semiconductor device according to any one of articles 1 to 6,the ring region of the first conductivity type is provided for each ofthe column circular regions of the second conductivity type.

8. The semiconductor device according to article 7 further includes: (l)a ring region of the second conductivity type provided in the surface ofthe drift region and outside the main junction region so as to surroundthe active cell region along an outer end of the column circular regionof the second conductivity type which is proximate to the ring region ofthe second conductivity type.

9. In the semiconductor device according to any one of articles 1 to 8,each of the peripheral corner regions is provided with a corner-portionsuper-junction structure having substantially the same width andorientation as those of the second super-junction structure.

10. In the semiconductor device according to any one of articles 1 to 8,the corner-portion super-junction structure has a trimmed outer portion.

11. A semiconductor device includes: (a) a semiconductor chip having afirst main surface provided with a source electrode of a power MOSFETand a second main surface provided with a drain electrode of the powerMOSFET; (b) a drift region of a first conductivity type provided insubstantially the entire first main surface of the semiconductor chip;(c) a substantially rectangular active cell region providedsubstantially at a middle portion of the first main surface, peripheralside regions provided outside the active cell region along individualsides of the active cell region, and peripheral corner regions providedoutside individual corner portions of the active cell region; (d) afirst super-junction structure having a first orientation and providedin substantially the entire surface of the cell region and in the driftregion; (e) second and third super-junction structures each having asecond orientation orthogonal to that of the first super-junctionstructure provided in the drift region of each of the peripheral sideregions on both sides of the active cell region in a direction of thefirst orientation of the first super-junction structure; (f) fourth andfifth super-junction structures each having an orientation substantiallythe same as that of the first super-junction structure and provided inthe drift region of each of the peripheral side regions on both sides ofthe active cell region in a direction orthogonal to the firstorientation of the first super-junction structure; (g) a main junctionregion of a second conductivity type which is an outer end portion ofthe active cell region and provided in a surface of the drift region soas to surround the active cell region; (h) a ring region of the firstconductivity type provided in the surface of the drift region andoutside the main junction region so as to surround the active cellregion along an inner end of a column circular region of the secondconductivity type which is proximate to the ring region of the firstconductivity type; and (i) a resin molded body covering substantiallythe entire first main surface of the semiconductor chip.

12. In the semiconductor device according to article 11, the ring regionof the first conductivity type is provided for each of the columncircular regions of the second conductivity type.

13. The semiconductor device according to article 11 or 12 furtherincludes: (j) a surface resurf region of the second conductivity typeprovided in the surface of the drift region so as to be coupled to anouter end of the main junction region and surround the main junctionregion.

14. The semiconductor device according to any one of articles 11 to 13further includes: (k) a plurality of floating field plates provided overthe first main surface via an insulating film and outside the mainjunction region so as to surround the active cell region

15. In the semiconductor device according to article 14, the floatingfield plates are provided for each of the column circular regions of thesecond conductivity type.

16. The semiconductor device according to any one of articles 11 to 15further includes: (l) a ring region of the second conductivity typeprovided in the surface of the drift region and outside the mainjunction region so as to surround the active cell region along an outerend of the column circular region of the second conductivity type whichis proximate to the ring region of the second conductivity type.

17. In the semiconductor device according to any one of articles 11 to16, each of the peripheral corner regions is provided with acorner-portion super-junction structure having substantially the samewidth and orientation as those of the second super-junction structure.

18. In the semiconductor device according to any one of articles 11 to16, the corner-portion super-junction structure has a trimmed outerportion.

19. In the semiconductor device according to any one of articles 11 to18, at least one of the floating field plates has a level difference inthe insulating film.

Next, a description will be given also to the outline of still otherembodiments (mainly related to a third part) of the invention disclosedin the present application.

1. A semiconductor device includes: (a) a semiconductor chip having afirst main surface provided with a source electrode of a power MOSFETand a second main surface provided with a drain electrode of the powerMOSFET; (b) a drift region of a first conductivity type provided insubstantially the entire first main surface of the semiconductor chip;(c) a substantially rectangular active cell region providedsubstantially at a middle portion of the first main surface, peripheralside regions provided outside the active cell region along individualsides of the active cell region, and peripheral corner, regions providedoutside individual corner portions of the active cell region; (d) afirst super-junction structure having a first orientation and providedin substantially the entire surface of the cell region and in the driftregion; (e) second and third super-junction structures each havingsubstantially the same width and orientation as those of the firstsuper-junction structure and provided in the drift region of each of theperipheral side regions on both sides of the active cell region in adirection of the first orientation of the first super-junction structureso as be coupled to the first super-junction structure; (f) fourth andfifth super-junction structures each having an orientation substantiallyorthogonal to that of the first super-junction structure and provided inthe drift region of each of the peripheral side regions on both sides ofthe active cell region in a direction orthogonal to the firstorientation of the first super-junction structure; (g) a main junctionregion of a second conductivity type which is an outer end portion ofthe active cell region and provided in a surface of the drift region soas to surround the active cell region; and (h) a corner-portionsuper-junction structure provided in the drift region in each of theperipheral corner regions. In the semiconductor device, thecorner-portion super-junction structure is laid out so as to maintainlocal charge balance.

2. The semiconductor device according to article 1 further includes: (i)a surface resurf region of the second conductivity type provided in thesurface of the drift region so as to be coupled to an outer end of themain junction region and surround the main junction region.

3. In the semiconductor device according to article 2, an outer end ofthe surface resurf region is located in a middle region between theouter end of the main junction region and an outer end of a peripheralsuper-junction region formed of the second to fifth super-junctionstructures.

4. In the semiconductor device according to article 2, the outer end ofthe surface resurf region is located substantially at a middle betweenthe outer end of the main junction region and the outer end of theperipheral super-junction region formed of the second to fifthsuper-junction structures.

5. In the semiconductor device according to any one of articles 1 to 4,the first to fifth super-junction structures and the corner-portionsuper-junction structure are formed by a trench epitaxial fillingmethod.

6. In the semiconductor device according to any one of articles 1 to 5,over the peripheral super-junction region formed of the second to fifthsuper-junction structures and the corner-portion super-junctionstructure, a plurality of floating field plates circularly extendingover the region are provided.

7. In the semiconductor device according to article 6, each of thefloating field plates shows a rectangular frame shape having cornerportions each bent at a right angle.

8. In the semiconductor device according to article 6, each of thefloating field plates shows a rectangular frame shape having cornerportions each roundly curved.

9. In the semiconductor device according to any one of articles 1 to 8,the corner-portion super-junction structure has a trimmed outer portion.

10. In the semiconductor device according to any one of articles 1 to 9,the corner-portion super-junction structure does not include amicro-column.

11. A semiconductor device includes: (a) a semiconductor chip having afirst main surface provided with a source electrode of a power MOSFETand a second main surface provided with a drain electrode of the powerMOSFET; (b) a drift region of a first conductivity type provided insubstantially the entire first main surface of the semiconductor chip;(c) a substantially rectangular active cell region providedsubstantially at a middle portion of the first main surface, peripheralside regions provided outside the active cell region along individualsides of the active cell region, and peripheral corner regions providedoutside individual corner portions of the active cell region; (d) afirst super-junction structure having a first orientation and providedin substantially the entire surface of the cell region and in the driftregion; (e) second and third super-junction structures each having asecond orientation orthogonal to that of the first super-junctionstructure provided in the drift region of each of the peripheral sideregions on both sides of the active cell region in a direction of thefirst orientation of the first super-junction structure; (f) fourth andfifth super-junction structures each having an orientation substantiallythe same as that of the first super-junction structure and provided inthe drift region of each of the peripheral side regions on both sides ofthe active cell region in a direction orthogonal to the firstorientation of the first super-junction structure; (g) a main junctionregion of a second conductivity type which is an outer end portion ofthe active cell region and provided in a surface of the drift region soas to surround the active cell region; and (h) a corner-portionsuper-junction structure provided in the drift region in each of theperipheral corner regions. In the semiconductor device, thecorner-portion super-junction structure is laid out so as to maintainlocal charge balance.

12. The semiconductor device according to article 11 further includes:(i) a surface resurf region of the second conductivity type provided inthe surface of the drift region so as to be coupled to an outer end ofthe main junction region and surround the main junction region.

13. The semiconductor device according to article 11 or 12 furtherincludes: (j) a plurality of floating field plates provided over thefirst main surface via an insulating film and outside the main junctionregion so as to surround the active cell region; and (k) a resin moldedbody covering substantially the entire first main surface of thesemiconductor chip.

14. In the semiconductor device according to article 13, each of thefloating field plates widthwise extends in a range covering an outer endportion of a column circular region of the second conductivity typewhich is proximate to the floating field plate, extending over a middleline of the column circular region of the second conductivity type, andnot extending over a vicinity of an inner end thereof closer to theactive cell region.

15. In the semiconductor device according to article 13 or 14, thefloating field plates are provided for each of the column circularregions of the second conductivity type.

16. In the semiconductor device according to any one of articles 11 to15, the first to fifth super-junction structures and the corner-portionsuper-junction structure are formed by a trench epitaxial fillingmethod.

17. In the semiconductor device according to any one of articles 13 to16, each of the floating field plates shows a rectangular frame shapehaving corner portions each bent at a right angle.

18. In the semiconductor device according to any one of articles 13 to16, each of the floating field plates shows a rectangular frame shapehaving corner portions each roundly curved.

19. The semiconductor device according to any one of articles 11 to 18,further includes: (l) a ring region of the first conductivity typeprovided in the surface of the drift region and outside the mainjunction region so as to surround the active cell region along an innerend of the column circular region of the second conductivity type whichis proximate to the ring region of the first conductivity type.

20. In the semiconductor device according to article 19, the ring regionof the first conductivity type is provided for each of the columncircular regions of the second conductivity type.

21. The semiconductor device according to any one of articles 11 to 20further includes: (m) a ring region of the second conductivity typeprovided in the surface of the drift region and outside the mainjunction region so as to surround the active cell region along the outerend of the column circular region of the second conductivity type whichis proximate to the ring region of the second conductivity type.

22. In the semiconductor device according to any one of articles 11 to21, the corner-portion super-junction structure has a trimmed outerportion.

23. In the semiconductor device according to any one of articles 11 to22, the corner-portion super-junction structure does not include amicro-column.

Explanation of Description Form, Basic Terminology, and Use Thereof inPresent Application

1. In the present application, if necessary for the sake of convenience,the description of an embodiment may be such that the embodiment isdivided into a plurality of parts or sections in the descriptionthereof. However, they are by no means independent of or distinct fromeach other unless particularly explicitly described otherwise, and oneof the individual parts of a single example is details, variations, andso forth of part or the whole of the others. In principle, a repeateddescription of like parts will be omitted. Each constituent element inthe embodiment is not indispensable unless particularly explicitlydescribed otherwise, unless the constituent element is theoreticallylimited to a given number, or unless it is obvious from the context thatthe constituent element is indispensable.

Also in the present application, when a “semiconductor device” ismentioned, it primarily refers to various stand-alone transistors(active elements) or to a device in which a resistor, a capacitor, andthe like are integrated around such a stand-alone transistor over asemiconductor chip or the like (e.g., a single-crystal siliconsubstrate). Representative examples of the various transistors that canbe shown include MISFETs (Metal Insulator Semiconductor Field EffectTransistors) represented by a MOSFET (Metal Oxide Semiconductor FieldEffect Transistor). Representative examples of the various stand-alonetransistors that can be shown include a power MOSFET and an IGBT(Insulated Gate Bipolar Transistor).

Note that, in the present application, a “semiconductor active element”indicates a transistor, a diode, or the like.

2. Likewise, even when such wording as “X comprised of A” is used inassociation with a material, a composition, or the like in thedescription of the embodiment or the like, it does not exclude amaterial, a composition, or the like which contains an element otherthan A as one of the main constituent elements thereof unlessparticularly explicitly described otherwise or unless it is obvious fromthe context that it excludes such a material, a composition, or thelike. For example, when a component is mentioned, the wording means “Xcontaining A as a main component” or the like. It will be appreciatedthat, even when, e.g., a “silicon member” or the like is mentioned, itis not limited to pure silicon, and a member containing a SiGe alloy,another multi-element alloy containing silicon as a main component,another additive, or the like is also included. Likewise, it will alsobe appreciated that, even when a “silicon oxide film”,“silicon-oxide-based insulating film”, or the like is mentioned, itincludes not only a relatively pure Undoped Silicon Dioxide, but also athermal oxide film of FSG (Fluorosilicate Glass), TEOS-based siliconoxide, SiOC (Silicon Oxicarbide), Carbon-doped Silicon oxide, OSG(Organosilicate glass), PSG (Phosphorus Silicate Glass), BPSG(Borophosphosilicate Glass), or the like, a CVD oxide film, a coatedsilicon oxide such as SOG (Spin ON Glass) or NCS (Nano-ClusteringSilica), a silica-based Low-k insulating film (porous insulating film)obtained by introducing voids into the same member as mentioned above, acomposite film with another silicon-based insulating film which containsany of these mentioned above as a main constituent element thereof, andthe like.

As a silicon-based insulating film commonly used in a semiconductorfield along with a silicon-oxide-based insulating film, there is asilicon-nitride-based insulating film. Materials belonging to thissystem include SiN, SiCN, SiNH, SiCNH, and the like. Here, when “siliconnitride” is mentioned, it includes both of SiN and SiNH unlessparticularly explicitly described otherwise. Likewise, when “SiCN” ismentioned, it includes both of SiCN and SiCNH unless particularlyexplicitly described otherwise.

SiC has properties similar to those of SiN while, in most cases, SiONshould rather be categorized into a silicon-oxide-based insulating film.

3. Likewise, it will also be appreciated that, although a preferredexample is shown in association with a graphical figure, a position, anattribute, or the like, the graphical figure, position, attribute, orthe like is not strictly limited thereto unless particularly explicitlydescribed otherwise or unless it is obvious from the context that thegraphical figure, position, attribute, or the like is strictly limitedthereto.

4. Further, when a specific numerical value or numerical amount ismentioned, it may be a value more or less than the specific numericalvalue unless particularly explicitly described otherwise, unless thenumerical value is theoretically limited to a given number, or unless itis obvious from the context that the numeral value is limited to a givennumber.

5. When a “wafer” is mentioned, it typically refers to a single-crystalsilicon wafer over which a semiconductor device (the same as asemiconductor integrated circuit device or an electronic device) isformed, but it will be appreciated that the “wafer” also includes acomposite wafer of an insulating substrate and a semiconductor layer orthe like, such as an epitaxial wafer, a SOI substrate, or an LCD glasssubstrate.

6. In general, a super-junction structure is such that, into asemiconductor region of a given conductivity type, columnar orplate-like column regions of the opposite conductivity type have beensubstantially equidistantly inserted so as to maintain charge balance.In the present application, when a “super-junction structure” formed bya trench fill method is mentioned, it refers to a structure in which,into a semiconductor region of a given conductivity type, plate-like“column regions” (which typically have plate-like shapes but may also becurved or bent) of the opposite conductivity type have beensubstantially equidistantly inserted in principle so as to maintaincharge balance. In the embodiment, a description will be given to astructure formed by equidistantly placing P-type columns in parallel inan N-type semiconductor layer (e.g., a drift region). The thicknesses Wp(of, e.g., FIG. 54) of the P-type columns in the individual portions maybe different from each other depending on the locations thereof but,when the super-junction structure is manufactured by the trench fillmethod, the P-type columns preferably have the same thickness Wp(width). This is because, if the widths of trenches are different, afilling property differs from portion to portion.

With regard to the super-junction structure, “orientation” indicates alongitudinal direction of a P-type column or an N-type column formingthe super-junction structure when the P-type or N-type column istwo-dimensionally viewed (in a plane parallel with the main surface of achip or wafer) in correspondence to the main surface of the chip.

Also, a “peripheral super-junction region” refers to a region which is aperipheral region outside an active cell region, i.e., an EdgeTermination Area and in which the super-junction structure is provided.

Also, in the present application, a structure in which the degree offreedom with which a depletion layer extends in the main region of theperipheral super-junction region (except for a part thereof includingcorners and the like) is 3 is referred to as a “3D-Resurf structure”,and a structure in which the degree of freedom is 2 is referred to as a“2D-Resurf structure”.

In the present application, in regard to a Resurf (Reduced SurfaceField) structure, a surface resurf region (specifically a “P⁻-typeresurf region” or “Junction Termination Extension”) refers to a regionformed in a surface area of a drift region, coupled to an end portion ofa P-type body region (P-type well region) forming a channel region, andhaving the same conductivity type as that of the P-type body region andan impurity concentration (concentration of a level at which the regionis completely depleted when a reverse voltage is applied to a mainjunction) lower than that thereof. Typically, the surface resurf regionis formed in a ring-like shape so as to surround a cell portion. Ageneral Field Plate refers to a portion which is a conductor filmpattern coupled to a source potential or a potential equivalent thereto,extends over the surface (device surface) of the drift region via aninsulating film, and surrounds the cell portion in a ring-likeconfiguration. On the other hand, a Floating Field Plate refers to afield plate similar to the general field plate, but is brought into afloating state.

Also, a Floating Field Ring or a Field Limiting Ring refers to animpurity region or a group of impurity regions each provided over thesurface (device surface) of the drift region separately from the P-typebody region (P-type well region), having the same conductivity type asthat of the P-type body region and a concentration similar to thatthereof (concentration of a level at which the impurity region is notcompletely depleted when a reverse voltage is applied to the mainjunction), and surrounding the cell portion in a single-ring ordouble-ring configuration.

Also, in the present application, the wording “maintain local chargebalance” indicates that, e.g., when the chip main surface istwo-dimensionally viewed, charge balance is achieved in a distance rangeof the order of the thickness (Wp or Wn) of the column.

Details of Embodiments

The embodiments will be described in greater detail. Hereinbelow, thedetails of the embodiments will be described by dividing the presentinvention into a plurality of parts. Unless particularly mentioned,“Sections”, “Embodiments”, and the like which are referenced refer tothose belonging to the same part in principle.

In the drawings, the same or like parts are designated by the same orsimilar marks or reference numerals, and a description thereof will notbe repeated in principle.

In the accompanying drawings, hatching or the like may be omitted evenin a cross section when hatching or the like results in complicatedillustration or when the distinction between a portion to be hatched anda vacant space is distinct. In relation thereto, even atwo-dimensionally closed hole may have a background outline thereofomitted when it is obvious from the description or the like that thehole is two-dimensionally closed, and so forth. On the other hand, eventhough not shown in a cross section, a portion other than a vacant spacemay be hatched to clearly show that the hatched portion is not a vacantspace.

Note that, for the convenience of illustration, the number of the P-typecolumns shown in each of the drawings is, e.g., about 3 to 5 in aperipheral side region or the like. However, the number of the P-typecolumns may actually exceed about 10 (it is considered that the numberof the P-type columns in the entire chip typically ranges from severalhundreds to several tens of hundreds but, for the convenience ofillustration, they are represented by a smaller number of the P-typecolumns). The example shown herein will be described by taking an itemhaving a breakdown voltage of about several hundred volts for instance.In the follow example, a product having a breakdown voltage of aboutseveral hundred volts (specifically, e.g., about 600 volts) will bedescribed by way of example.

Note that examples of a patent application concerning a MOSFET having asuper-junction structure filed by the present inventors include JapanesePatent Application No. 2009-263600 (filed on Nov. 19, 2009), JapanesePatent Application No. 2010-109957 (filed on May 12, 2010), JapanesePatent Application No. 2010-81905 (filed on Mar. 31, 2010), and thelike.

<First Part: Portion Mainly Related to 3D-Resurf Structure>

0. Outline of First Part

In regard to a drift region in a power MOSFET or the like, it has beenan important task to avoid restrictions imposed by a related-art SiliconLimit and develop a high-breakdown-voltage FET having a lowON-resistance or the like. To achieve the task, various methods havebeen developed which introduce a super-junction structure alternatelyhaving relatively-high-concentration Slab-like N-type columns and P-typecolumns into the drift region. The methods which introduce thesuper-junction structure are roughly divided into three types ofmethods, i.e., the multi-epitaxial method, the trench insulating filmfilling method, and a trench fill method (trench filling method ortrench epitaxial filling method). Among them, the multi-epitaxial methodin which epitaxial growth and ion implantation are repeated multipletimes has high process and design flexibility and accordinglycomplicated process steps, resulting in high cost. In the trenchinsulating film filling method, after oblique ion implantation intotrenches is performed, the trenches are filled with a CVD (ChemicalVapor Deposition) insulating film. The trench insulating film fillingmethod is simpler in terms of process, but is disadvantageous in termsof area due to the area of the trenches.

By contrast, the trench fill method has relatively low process anddesign flexibility due to constraints on growth conditions for fillingepitaxial growth, but has the advantage of simple process steps. In viewof this, the present inventors have studied problems associated with adevice structure and mass production of a power MOSFET or the like inrelation to a high breakdown voltage and a low ON-resistance to beachieved by the trench fill method or the like and found the followingproblem. That is, in the super-junction structure, the concentration ofa main body cell portion (active region) is relatively high, andtherefore it is difficult to ensure a breakdown voltage equal to orhigher than that of the cell portion for a peripheral portion(peripheral region or junction termination area) using a related-artedge termination structure (Junction Edge Termination Structure) or arelated-art Resurf (Reduced Surface Field) Structure. Specifically, theproblem is such that, in an outer peripheral corner portion of a chip,due to electric field concentration, variations in breakdown voltagebecome sensitive to charge unbalance in the super-junction structure.

The following is a brief description of the outline of a representativeembodiment of the invention disclosed in the present part.

That is, according to an aspect of the invention in the present part, ina semiconductor power device such as a power MOSFET having asuper-junction structure in each of an active cell region and a chipperipheral region, an outer end of a surface resurf region of a secondconductivity type coupled to a main junction (impurity regionsurrounding the active cell region and integrated with a channel region)of the second conductivity type in a surface of a drift region of afirst conductivity type and having a concentration lower than that ofthe main junction is located in a middle region between an outer end ofthe main junction and an outer end of the super-junction structure inthe chip peripheral region.

The following is a brief description of an effect obtained according tothe representative embodiment of the invention disclosed in the presentpart.

That is, in a semiconductor power device such as a power MOSFET having asuper-junction structure in each of an active cell region and a chipperipheral region, an outer end of a surface resurf region of a secondconductivity type coupled to a main junction (impurity regionsurrounding the active cell region and integrated with a channel region)of the second conductivity type in a surface of a drift region of afirst conductivity type and having a concentration lower than that ofthe main junction is located in a middle between an outer end of themain junction and an outer end of the super-junction structure in thechip peripheral region to allow a position where an electric field isconcentrated to be located away from the outer end of the super-junctionstructure.

1. Description of Device Structure (Peripheral 3D Super-Junction andHalf-Range P− Resurf Layer) of Power MOSFET with Super-JunctionStructure, Etc. as Example of Semiconductor Device of First Embodimentof Present Invention (See Mainly FIGS. 1 to 7)

In this example, a specific description will be given using a planarpower MOSFET formed in a silicon-based semiconductor substrate andhaving a source/drain breakdown voltage of about 600 volts as an example(with regard to the planar power MOSFET, the same also holds true in thefollowing sections). However, it will be appreciated that the presentinvention is also applicable to a power MOSFET having another breakdownvoltage value and other devices.

FIG. 1 is a top view of an entire chip (mainly of a surface regionthereof) of a power MOSFET having a super-junction structure as anexample of a semiconductor device of a first embodiment (peripheral 3Dsuper-junction and half-range P− resurf layer) of the present invention.FIG. 2 is a top view of the entire chip (mainly of an impurity dopedstructure thereof or the like) of the power MOSFET having thesuper-junction structure as the example of the semiconductor device ofthe first embodiment of the present invention. FIG. 3 is a top view(closer to a real equivalent) of a local portion of the chipcorresponding to a cut-away region R1 of the chip corner portion ofFIG. 1. FIG. 4 is a top view (schematic diagram for illustration) of thelocal portion of the chip corresponding to the cut-away region R1 of thechip corner portion of FIG. 1. FIG. 5 is a cross-sectional view of alocal portion of the chip corresponding to the X-X′ cross section ofFIG. 4. FIG. 6 is a cross-sectional view of a local portion of the chipcorresponding to the Y-Y′ cross section of FIG. 4. FIG. 7 is across-sectional view of a local portion of the chip (corresponding totwo active cells) corresponding to the A-A′ cross section of a cut-awayregion R2 of the active cell portion of FIG. 1. Based on these drawings,a description will be given to a device structure (peripheral 3Dsuper-junction and half-range P− resurf layer) of the power MOSFEThaving the super-junction structure or the like as the example of thesemiconductor device of the first embodiment of the present invention.

First, a description will be given to a schematic layout of the uppersurface of the chip (typically several millimeters square). As shown inFIG. 1, in a power MOSFET element chip 2 in which elements are formedover a silicon-based semiconductor substrate (which is a wafer 1 beforebeing divided into the individual chips 2) in the form of a square orrectangular plate, a metal source electrode 5 (aluminum-based electrode)located in a center portion occupies a major area. Under the metalsource electrode 5, an active cell region 4 is provided, and the outerend portion thereof is a P-type main junction 6 (the outer edge portionof a P body region. Note that the super-junction structure, under activecells extends under substantially the entire P-type main junction 6).Inside the P-type main junction 6, a repetitive structure portion 4 r ofthe active cell region 4 (the P body region is formed in the surfacearea of the entire repetitive structure portion 4 r located between gateelectrodes and shows a two-dimensional multifoil structure from whichgate electrode portions are periodically and slitwise missing) isprovided. Outside the ring-like P-type main junction 6, a P⁻-typesurface resurf region 8 similarly having a ring-like shape is provided.In addition, over a region including the P⁻-type surface resurf region 8and an outside region thereof, a peripheral super-junction region 9(region where linear P columns 12 p and an N-type drift region 11 nlocated therebetween are periodically and substantially equidistantlyarranged in a peripheral drift region 11 or a combined region thereof)is provided. Here, the outer end of the P⁻-type surface resurf region 8is located in a middle region between an outer end 9 e of the peripheralsuper-junction region 9 and the outer end of the P-type main junction 6.More preferably, the outer end of the P⁻-type surface resurf region 8 issubstantially at a middle between the outer end 9 e of the peripheralsuper-junction region 9 and the outer end of the P-type main junction 6.

Further, around the peripheral super-junction region 9, analuminum-based metal guard ring 3 is provided. Between thealuminum-based metal guard ring 3 and the metal source electrode 5, ametal gate electrode 7 for retrieving polysilicon gate electrodes to theoutside is provided. Note that, in FIG. 1 (the same also holds true inFIGS. 2 to 4), the metal gate electrode 7 is exaggeratingly depictedwider than the real equivalent for easy understanding of a structure ofthe Edge Termination Area.

Next, a description will be given to a two-dimensional diffusionstructure of the chip 2 and a device layout thereof. As shown in FIG. 2,in a center portion of the chip 1, the active cell region 4 (under whichan active-cell-portion super-junction structure 14, i.e., a firstsuper-junction structure exists) is provided. Inside the active cellregion 4, a large number of linear polysilicon gate electrodes 15 areprovided. In addition, outside the ring-like P-type main junction 6which is the outer edge portion of the active cell region 4 andsurrounds the active cell region 4, the ring-like P⁻-type surface resurfregion 8 coupled to the P-type main junction 6 and surrounding theactive cell region 4 is provided.

Next, a description will be given to a super-junction structure aroundthe active-cell-portion super-junction structure 14, i.e., the firstsuper-junction structure, i.e., the peripheral super-junction structure9 (FIG. 1). In peripheral side regions 16 a and 16 c, a secondsuper-junction structure 18 and a third super-junction structure 19 eachof which is coupled to the active-cell-portion super-junction structure14 and has the same orientation as that of the active-cell-portionsuper-junction structure 14 are provided. On the other hand, inperipheral side regions 16 b and 16 d, a fourth super-junction structure21 and a fifth super-junction structure 22 each of which is not coupledto the active-cell-portion super-junction structure 14 and has anorientation orthogonal to that of the active-cell-portion super-junctionstructure 14 are provided. Note that, in the column layout, individualperipheral corner regions 17 a, 17 b, 17 c, and 17 d form periodicextension regions of the peripheral side regions 16 b and 16 d locatedtherebelow or thereabove.

FIG. 3 shows an enlarged view of the portion of FIG. 2 corresponding tothe cutaway region R1 of the chip corner portion of FIG. 1. As shown inFIG. 3, the outer end of the P⁻-type surface resurf region 8 issubstantially at a middle between the outer end 9 e of the peripheralsuper-junction region 9 and the outer end of the P-type main junction 6around the entire periphery thereof.

Next, FIG. 4 is a more schematic depiction of FIG. 3 (in which thenumber of the P columns 12 p is reduced to clearly show the relationsamong individual elements). As shown in FIG. 4, the repetitive structureportion 4 r in the active cell region is provided with a periodicstructure (one-dimensional periodic structure) in which P+ body contactregions 23 and the polysilicon gate electrodes 15 alternately repeat.The thickness Wn (or width) of each N column is, e.g., about 6micrometers, and the thickness Wp (or width) of each P column is, e.g.,about 4 micrometers. Accordingly, the pitch of the super-junction isabout 10 micrometers. In this example, the thickness Wn (or width) ofthe N column and the thickness Wp (or width) of the P column aresubstantially constant in the entire chip region 2. Such parameters mayalso be varied depending on locations. However, in the trench fillmethod, substantially constant parameters are advantageous in terms ofprocess. The impurity (e.g., antimony) concentration of each of the Ncolumns 12 n is, e.g., about 3.3×10¹⁵/cm³, and the impurity (e.g.,boron) concentration of each of the P columns 12 p is, e.g., about5.0×10¹⁵/cm³.

FIG. 5 shows the X-X′ cross section of FIG. 4, while FIG. 6 shows theY-Y′ cross section of FIG. 4. As shown in FIGS. 5 and 6, on the surfaceof an N+ drain region 25 (N-type single-crystal silicon substrate) of aback surface 1 b of the chip 2, a metal back-surface drain electrode 24is provided. Over the N+ drain region 25, the drift region 11 isprovided and formed of the N columns 12 n, the P columns 12 b (P-typedrift regions), the N-type drift region 11 n, and the like. In thesurface area of the drift region 11, the P-type main junction 6 (P well,P body region, or the outer edge portion thereof) is provided. In the Pbody region 6, N+ source regions 26, the P+ body contact regions 23, andthe like are provided. Outside the P-type main junction 6, the P⁻-typesurface resurf region 8 is provided to be coupled thereto. In thesurface area of the N-type drift region 11 n in an end portion of thechip 2, an N+ channel stop region 31, a P+ chip peripheral contactregion 32, and the like are provided. Over a semiconductor surfacebetween the pair of N+ source regions 26, the polysilicon gate electrode15 is provided via a gate insulating film 27. Over the polysilicon gateelectrode 15 and a field insulating film 34, an interlayer insulatingfilm 29 is provided. Over the interlayer insulating film 29,aluminum-based electrode films including the metal source electrode 5and the metal guard ring 3 are formed and each electrically coupled tothe P+ body contact regions 23, the N+ channel stop region 31, the P+chip peripheral contact region 32, or the like. Note that the respectivewidths (thicknesses) of the N column 12 n and the P column 12 p are,e.g., about 6 micrometers and about 4 micrometers. The respective dosesof the N column 12 n and the P column 12 p are, e.g., about 3.3×10¹⁵/cm³and about 5.0×10¹⁵/cm³.

FIG. 7 shows the A-A′ cross section (corresponding to 2 periods of therepetitive structure) of the cutaway region R2 of the active cellportion of FIG. 1. As shown in FIG. 7, on the surface of the N+ drainregion 25 (N-type single-crystal silicon substrate) of the back surface1 b of the chip 2, the metal back-surface drain electrode 24 isprovided. Over the N+ drift region 25, the drift region 11 is providedand formed of the N columns 12 n (N-type drift region 11 n) and the Pcolumns 12 p (P-type drift region 11 p). In the surface area of thedrift region 11, the P body region 6 is provided. In the P body region6, the N+ source regions 26, the P+ body contact regions 23, and thelike are provided. Over the semiconductor surface between the pair of N+source regions 26, the polysilicon gate electrode 15 is provided via thegate insulating film 27. Over the polysilicon gate electrode 15, theinterlayer insulating film 29 is provided. Over the interlayerinsulating film 29, the aluminum-based electrode films including themetal source electrode 5 are formed and electrically coupled to the P+body contact regions 23.

2. Description of Wafer Process Corresponding to Semiconductor Device ofFirst Embodiment of Present Invention, Etc. (See Mainly FIGS. 8 to 22)

In this section, a process corresponding to the structure of the firstsection will be described. However, these process steps are basicallycommon to other structures so that the following description will not berepeated in principle for the other structures.

FIG. 8 is a wafer cross-sectional view of a device portion shown in FIG.5 for illustrating a wafer process (step of forming trenches)corresponding to the semiconductor device of the first embodiment of thepresent invention. FIG. 9 is a wafer cross-sectional view of the deviceportion shown in FIG. 5 for illustrating the wafer process (step ofremoving a hard mask for forming the trenches) corresponding to thesemiconductor device of the first embodiment of the present invention.FIG. 10 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of filling the trencheswith a P-type epitaxial layer) corresponding to the semiconductor deviceof the first embodiment of the present invention. FIG. 11 is a wafercross-sectional view of the device portion shown in FIG. 5 forillustrating the wafer process (CMP step) corresponding to thesemiconductor device of the first embodiment of the present invention.FIG. 12 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of introducing theP⁻-type surface resurf region) corresponding to the semiconductor deviceof the first embodiment of the present invention. FIG. 13 is a wafercross-sectional view of the device portion shown in FIG. 5 forillustrating the wafer process (step of patterning the field oxide film)corresponding to the semiconductor device of the first embodiment of thepresent invention. FIG. 14 is a wafer cross-sectional view of the deviceportion shown in FIG. 5 for illustrating the wafer process (step ofintroducing the P body region) corresponding to the semiconductor deviceof the first embodiment of the present invention. FIG. 15 is a wafercross-sectional view of the device portion shown in FIG. 5 forillustrating the wafer process (step of forming the gate insulatingfilm) corresponding to the semiconductor device of the first embodimentof the present invention. FIG. 16 is a wafer cross-sectional view of thedevice portion shown in FIG. 5 for illustrating the wafer process (stepof forming a gate polysilicon film) corresponding to the semiconductordevice of the first embodiment of the present invention. FIG. 17 is awafer cross-sectional view of the device portion shown in FIG. 5 forillustrating the wafer process (step of patterning the gate polysiliconfilm into the gate electrodes) corresponding to the semiconductor deviceof the first embodiment of the present invention. FIG. 18 is a wafercross-sectional view of the device portion shown in FIG. 5 forillustrating the wafer process (step of forming the source regions)corresponding to the semiconductor device of the first embodiment of thepresent invention. FIG. 19 is a wafer cross-sectional view of the deviceportion shown in FIG. 5 for illustrating the wafer process (step offorming the interlayer insulating film) corresponding to thesemiconductor device of the first embodiment of the present invention.FIG. 20 is a wafer cross-sectional view of the device portion shown inFIG. 5 for illustrating the wafer process (step of forming contactholes) corresponding to the semiconductor device of the first embodimentof the present invention. FIG. 21 is a wafer cross-sectional view of thedevice portion shown in FIG. 5 for illustrating the wafer process (stepof extending the contact holes and introducing the body contact regions)corresponding to the semiconductor device of the first embodiment of thepresent invention. FIG. 22 is a wafer cross-sectional view of the deviceportion shown in FIG. 5 for illustrating the wafer process (step offorming an aluminum-based conductive film) corresponding to thesemiconductor device of the first embodiment of the present invention.Based on these drawings, a description will be given to a wafer processcorresponding to the semiconductor device of the first embodiment of thepresent invention or the like.

First, as shown in FIG. 8, the semiconductor wafer 1 is prepared inwhich, over the N-type single-crystal silicon substrate 25 (which is,e.g., a 200 mm wafer but may also have a wafer diameter of 150 mm, 300mm, or 450 mm) doped with, e.g., antimony (at a concentration of theorder of, e.g., about 10¹⁸/cm³ to 10¹⁹/cm³), a phosphorus-dopedN-epitaxial layer 10 n (drift region at a concentration of the order of,e.g., about 10¹⁵/cm³, which is a portion serving as the N-type driftregion 11 n and also partly serving as the N columns 12 n) having athickness of, e.g., about 45 micrometers is formed. Over a devicesurface 1 a (main surface opposite to the back surface 1 b) of thesemiconductor wafer 1, a hard mask film 33 for forming P-type columntrenches made of, e.g., P-TEOS (Plasma-Tetraethylorthosilicate) or thelike is formed. Next, as shown in FIG. 8, using the hard mask 33 forforming P-type column trenches as a mask, the N epitaxial layer 10 n andthe like are dry-etched to form P-type column trenches 20. Examples of adry etching atmosphere that can be shown include an atmospherecontaining, e.g., Ar, SF₆, O₂, and so forth as main gas components.Examples of the range of the depth of dry etching that can be showninclude a range of, e.g., about 40 to 55 micrometers. Note that theP-type column trenches 20 preferably reach the N-type single-crystalsilicon substrate 25. However, the P-type column trenches 20 need notnecessarily reach the N-type single-crystal silicon substrate 25 as longas they are proximate thereto.

Next, as shown in FIG. 9, the hard mask 33 that is no longer needed isremoved.

Next, as shown in FIG. 10, filling epitaxial growth (in-trench epitaxialfilling method) is performed with respect to the P-type column trenches20 to form a P-type filling epitaxial layer 10 p (dopant is boron at aconcentration of the order of, e.g., about 10¹⁵/cm³). The P-typeepitaxial region 10 p is a portion serving as the P-type drift region 11p and also serving as the P columns 12 p. Examples of conditions for thefilling epitaxial growth that can be shown include a processing pressureof, e.g., about 1.3×10⁴ Pascal to 1.0×10⁵ Pascal, a raw material gas ofsilicon tetrachloride, trichlorosilane, dichlorosilane, monosilane, orthe like.

Next, as shown in FIG. 11, the P-type filling epitaxial layer 10 plocated outside the P-type column trenches 20 is removed by aplanarizing step, e.g., CMP (Chemical Mechanical Polishing), while thesurface 1 a of the semiconductor wafer 1 is simultaneously planarized.Note that, here, a super-junction structure as shown in FIG. 11 may alsobe formed by a multi-epitaxial method besides the trench fill method.

Next, as shown in FIG. 12, the silicon oxide film 34 (field insulatingfilm) is formed by thermal oxidation over substantially the entire topsurface 1 a of the semiconductor wafer 1, and a resist film 35 forintroducing P⁻-type resurf region is formed thereover by lithography.Examples of the thickness of the field insulating film 34 that can beshown include about 350 nm.

Subsequently, using the resist film 35 for introducing P⁻-type resurfregion as a mask, the P⁻-type surface resurf region 8 is introduced byion implantation (of, e.g., boron). Examples of conditions for the ionimplantation that can be shown include an ion species of boron, animplantation energy in a preferred range around, e.g., 200 keV, and adose in a preferred range of, e.g., about 1×10¹¹/cm² to 1×10¹²/cm².Thereafter, the resist film 35 that is no longer needed is removed.

Next, as shown in FIG. 13, over the top surface 1 a of the semiconductorwafer 1, a resist film 36 for etching silicon oxide film is formed bylithography. Subsequently, using the resist film 36 as a mask, the fieldinsulating film 34 is patterned by dry etching using, e.g., afluorocarbon-based etching gas or the like. Thereafter, the resist film36 that is no longer needed is entirely removed.

Next, as shown in FIG. 14, a resist film 37 for introducing P bodyregion is formed over the top surface 1 a of the semiconductor wafer 1by lithography (typically, prior to the formation of the resist film 37,a protective film against ion implantation such as a thermal oxidationfilm of, e.g., about 10 nm is formed over the top surface 1 a of thesemiconductor wafer 1, but a depiction thereof is omitted to preventcomplicated illustration, which is also the same in other portions).Subsequently, using the resist film 37 for introducing P body region asa mask, the P body region 6 is introduced by ion implantation. Examplesof conditions for the ion implantation that can be shown include: (1) anion species of boron, an implantation energy in a preferred rangearound, e.g., 200 keV, and a dose in a preferred range around the orderof, e.g., 10¹³/cm², which are for a first step; and (2) an ion speciesof boron, an implantation energy in a preferred range around, e.g., 75keV, and a dose in a preferred range around the order of, e.g., 10¹²/cm²(a concentration is on the order of, e.g., about 10¹⁷/cm³), which arefor a second step. Thereafter, as shown in FIG. 14, the resist film 37that is no longer needed is entirely removed.

Next, as shown in FIG. 15, over the top surface 1 a of the semiconductorwafer 1, the gate oxide film 27 (gate insulating film) is formed. Anexemplary thickness of the gate insulating film 27 that can be shownranges from, e.g., about 50 nm to 200 nm, though it depends on abreakdown voltage. Examples of film deposition method that can be showninclude a CVD (Chemical Vapor Deposition), a thermal oxidation method,and the like. Note that, to wafer cleaning prior to gate oxidation, wetcleaning can be applied which uses, e.g., a first cleaning solution,i.e., a mixed solution of ammonia, hydrogen peroxide, and pure water at1:1:5 (volume ratio) and a second cleaning solution, i.e., a mixedsolution of hydrochloric acid, hydrogen peroxide, and pure water at1:1:6 (volume ratio).

Next, as shown in FIG. 16, over the gate oxide film 27, a gate electrodepolysilicon film 15 (having a thickness of, e.g., about 200 nm to 800nm) is formed by, e.g., low-pressure CVD (Chemical Vapor Deposition).

Next, as shown in FIG. 17, the gate electrode polysilicon film 15 ispatterned by dry etching into the gate electrodes 15.

Next, as shown in FIG. 18, a resist film 38 for introducing N+ sourceregions is formed by lithography and, using the resist film 38 as amask, the N+ source regions 26 and the N+ channel stopper region 31 inthe chip edge portion are introduced by ion implantation. Examples ofconditions for the ion implantation that can be shown include an ionspecies of arsenic, an implantation energy in a preferred range around,e.g., 40 keV, and a dose in a preferred range around the order of, e.g.,10¹⁵/cm² (a concentration is on the order of, e.g., about 10²⁰/cm³).Thereafter, the resist film 38 that is no longer needed is entirelyremoved.

Next, as shown in FIG. 19, over substantially the entire surface of thetop surface 1 a of the semiconductor wafer 1, the PSG(Phospho-Silicate-Glass) film 29 (interlayer insulating film) isdeposited by CVD or the like. Note that, as the interlayer insulatingfilm 29, a BPSG film, a TEOS film, a SOG film, a HDP (High DensityPlasma) silicon oxide film, a PSG film, or a laminate film of aplurality of any of the foregoing films may also be used besides the PSGfilm. Preferred examples of the total thickness of the interlayerinsulating film 29 that can be shown include about 900 nm.

Next, as shown in FIG. 20, over the top surface 1 a of the semiconductorwafer 1, a resist film 41 for forming source contact holes is formedand, using the resist film 41 as a mask, source contact holes 39 and thelike are opened by dry etching. Subsequently, the resist film 41 that isno longer needed is entirely removed.

Next, as shown in FIG. 21, the silicon substrate is etched and then, byion implantation, the P+ body contact regions 23 and the P+ chipperipheral contact region 32 are introduced. Examples of conditions forion implantation that can be shown include an ion species of BF₂, animplantation energy in a preferred range around, e.g., 30 keV, and adose in a preferred range around the order of, e.g., 10¹⁵/cm² (aconcentration is on the order of, e.g., about 10¹⁹/cm³).

Next, as shown in FIG. 22, an aluminum-based metal layer is deposited bysputtering or the like via a barrier metal film of TiW or the like andpatterned to form the metal source electrode 5, the guard ring electrode3, and the like.

Then, as necessary, a final passivation film such as, e.g., an inorganicfinal passivation film or an organic-inorganic final passivation film isformed in an upper layer, and pad openings and gate openings are formedtherein. As the final passivation film, a single-layer film such as aninorganic final passivation film or an organic-inorganic finalpassivation film may be formed or, besides, an organic-inorganic finalpassivation film or the like may also be laminated over an under-layerinorganic final passivation film.

Next, a back grinding treatment is performed to reduce the originalwafer thickness (e.g., about 750 micrometers) to, e.g., about 80 to 280micrometers (i.e., a thickness less than 300 micrometers).

In addition, over the back surface 1 b of the wafer 1, the metalback-surface drain electrode 24 (see FIGS. 5 to 7) is deposited bysputtering film deposition. The back-surface metal electrode film 24includes, e.g., a back-surface titanium film (diffusion preventing layerof gold and nickel), a back-surface nickel film (adhesive layer to achip bonding material), a back-surface gold film (oxidation preventinglayer of nickel) which are mentioned in order of increasing distancefrom the wafer 1, and the like. Thereafter, the wafer 1 is divided intoindividual chips, resulting in a device as shown in FIG. 1.

3. Description of Device Structure (Peripheral 3D Super-Junction,Half-Range P− Resurf Layer, and Floating Field Plates) of Power MOSFETwith Super-Junction Structure, Etc. as Example of Semiconductor Deviceof Second Embodiment of Present Invention (See Mainly FIGS. 23 to 26)

An example described in this section is the same as the structuredescribed in the first section (e.g., FIGS. 1, 2, and 7 are the same)except for floating field plates so that a description will be givenonly to a different portion. In a device which does not have asuper-junction structure in the periphery thereof, it is normallyeffective to dispose a ring-like floating field ring (field limitingring) in a single-ring or double-ring configuration and thereby preventundesired electric field concentration. However, in a device having asuper-junction structure, it is generally difficult to use a floatingfield ring which is not completely depleted when a reverse voltage isapplied to a main junction (in an OFF state). Therefore, here, adescription will be given to the use of floating field plates as areplacement.

FIG. 23 (corresponding to FIG. 3) is a top view (closer to a realequivalent) of a local portion of a chip corresponding to the cut-awayregion R1 of the chip corner portion of FIG. 1 of a power MOSFET havinga super-junction structure as an example of a semiconductor device of asecond embodiment (peripheral 3D super-junction, half-range P− resurflayer, and floating field plates) of the present invention. FIG. 24(corresponding to FIG. 4) is a top view (schematic diagram forillustration) of the local portion of the chip corresponding to thecut-away region R1 of the chip corner portion shown in FIG. 23. FIG. 25(corresponding to FIG. 5) is a cross-sectional view of a local portionof the chip corresponding to the X-X′ cross section of FIG. 24. FIG. 26(corresponding to FIG. 6) is a cross-sectional view of a local portionof the chip corresponding to the Y-Y′ cross section of FIG. 24. Based onthese drawings, a description will be given to a device structure(peripheral 3D super-junction, half-range P− resurf layer, and floatingfield plates) of a power MOSFET having a super-junction structure or thelike as an example of the semiconductor device of the second embodimentof the present invention.

As shown in FIGS. 23 to 26, ring-like floating field plates 30 extendingaround the active cell region 4 (P-type main junction 6) are arranged ina multiple ring configuration to thereby reduce electric fieldconcentration in the surface area of the drift region 11 withoutimpairing the function of the super-junction structure. In this example,the floating field plates 30 are formed of, e.g., the same polysiliconlayer as that of each of the gate polysilicon electrodes 15 so that ahigh-concentration impurity (e.g., phosphorus or arsenic in the case ofadding an N-type impurity) has been added thereto. As shown in FIGS. 25and 26, the floating field plates 30 are provided over, e.g., the fieldoxide film 34. Note that, since the plan configuration of each of thefloating field plates 30 extends along the periphery of the chip 2, ithas a substantially rectangular frame shape (ring shape), but the cornerportions thereof may be rounded or shaped otherwise as necessary.

4. Description of Wafer Process Corresponding to Semiconductor device ofsecond embodiment of present invention, Etc. (See Mainly FIGS. 27 to 33)

Basically, a process in this section is substantially the same as in thesecond section so that, hereinbelow, a description will be given only toa different portion. That is, FIGS. 8 to 15 are completely the same sothat the description thereof will not be repeated. Therefore, thefollowing description starts from the completion of the formation of thegate insulating film in FIG. 15.

FIG. 27 is a wafer cross-sectional view (corresponding to FIG. 16 of thefirst embodiment) of the device portion shown in FIG. 25 forillustrating a wafer process (step of forming a gate polysilicon film)corresponding to the semiconductor device of the second embodiment ofthe present invention. FIG. 28 is a wafer cross-sectional view(corresponding to FIG. 17 of the first embodiment) of the device portionshown in FIG. 25 for illustrating the wafer process (step of patterningthe gate polysilicon film into the gate electrodes) corresponding to thesemiconductor device of the second embodiment of the present invention.FIG. 29 is a wafer cross-sectional view (corresponding to FIG. 18 of thefirst embodiment) of the device portion shown in FIG. 25 forillustrating the wafer process (step of forming source regions)corresponding to the semiconductor device of the second embodiment ofthe present invention. FIG. 30 is a wafer cross-sectional view(corresponding to FIG. 19 of the first embodiment) of the device portionshown in FIG. 25 for illustrating the wafer process (step of forming aninterlayer insulating film) corresponding to the semiconductor device ofthe second embodiment of the present invention. FIG. 31 is a wafercross-sectional view (corresponding to FIG. 20 of the first embodiment)of the device portion shown in FIG. 25 for illustrating the waferprocess (step of forming contact holes) corresponding to thesemiconductor device of the second embodiment of the present invention.FIG. 32 is a wafer cross-sectional view (corresponding to FIG. 21 of thefirst embodiment) of the device portion shown in FIG. 25 forillustrating the wafer process (step of extending the contact holes andintroducing body contact regions) corresponding to the semiconductordevice of the second embodiment of the present invention. FIG. 33 is awafer cross-sectional view (corresponding to FIG. 22 of the firstembodiment) of the device portion shown in FIG. 25 for illustrating thewafer process (step of forming an aluminum-based conductive film)corresponding to the semiconductor device of the second embodiment ofthe present invention. Based on these drawings, a description will begiven to a wafer process corresponding to the semiconductor device ofthe second embodiment of the present invention.

Next, as shown in FIG. 27, over the gate oxide film 27, the gateelectrode polysilicon film 15 (having a thickness of, e.g., about 200 nmto 800 nm) is formed by, e.g., low-pressure CVD (Chemical VaporDeposition).

Next, as shown in FIG. 28, the gate electrode polysilicon film 15 ispatterned by dry etching into the gate electrodes 15 and the floatingfield plates 30.

Next, as shown in FIG. 29, the resist film 38 for introducing N+ sourceregions is formed by lithography and, using the resist film 38 as amask, the N+ source regions 26 and the N+ channel stopper region 31 inthe chip edge portion are introduced by ion implantation. Examples ofconditions for the ion implantation that can be shown include an ionspecies of arsenic, an implantation energy in a preferred range around,e.g., 40 keV, and a dose in a preferred range around the order of, e.g.,10¹⁵/cm² (a concentration is on the order of, e.g., about 10²⁰/cm³).Thereafter, the resist film 38 that is no longer needed is entirelyremoved.

Next, as shown in FIG. 30, over substantially the entire surface of thetop surface 1 a of the semiconductor wafer 1, the PSG(Phospho-Silicate-Glass) film 29 (interlayer insulating film) isdeposited by CVD or the like. Note that, as the interlayer insulatingfilm 29, a BPSG film, a TEOS film, a SOG film, a HDP (High DensityPlasma) silicon oxide film, a PSG film, or a laminate film of aplurality of any of the foregoing films may also be used besides the PSGfilm. Preferred examples of the total thickness of the interlayerinsulating film 29 that can be shown include about 900 nm.

Next, as shown in FIG. 31, over the top surface 1 a of the semiconductorwafer 1, the resist film 41 for forming source contact holes is formedand, using the resist film 41 as a mask, the source contact holes 39 andthe like are opened by dry etching. Subsequently, the resist film 41that is no longer needed is entirely removed.

Next, as shown in FIG. 32, the silicon substrate is etched and then, byion implantation, the P+ body contact regions 23 and the P+ chipperipheral contact region 32 are introduced. Examples of conditions forion implantation that can be shown include an ion species of BF₂, animplantation energy in a preferred range around, e.g., 30 keV, and adose in a preferred range around the order of, e.g., 10¹⁵/cm² (aconcentration is on the order of, e.g., about 10¹⁹/cm³).

Next, as shown in FIG. 33, an aluminum-based metal layer is deposited bysputtering or the like via a barrier metal film of TiW or the like andpatterned to form the metal source electrode 5, the guard ring electrode3, and the like.

Then, as necessary, a final passivation film such as, e.g., an inorganicfinal passivation film or an organic-inorganic final passivation film isformed in an upper layer, and pad openings and gate openings are formedtherein. As the final passivation film, a single-layer film such as aninorganic final passivation film or an organic-inorganic finalpassivation film may be formed or, besides, an organic-inorganic finalpassivation film or the like may also be formed over an under-layerinorganic final passivation film.

Next, a back grinding treatment is performed to reduce the originalwafer thickness (e.g., about 750 micrometers) to, e.g., about 80 to 280micrometers (i.e., a thickness less than 300 micrometers).

In addition, over the back surface 1 b of the wafer 1, the metalback-surface drain electrode 24 (see FIGS. 7, 25, and 26) is depositedby sputtering film deposition. The back-surface metal electrode film 24includes, e.g., a back-surface titanium film (diffusion preventing layerof gold and nickel), a back-surface nickel film (adhesive layer to achip bonding member), a back-surface gold layer (oxidation preventinglayer of nickel) which are mentioned in order of increasing distancefrom the wafer 1, and the like. Thereafter, the wafer 1 is divided intoindividual chips, resulting in a device as shown in FIG. 1.

5. Description of Variations of Individual Components in SemiconductorDevices of First and Second Embodiments of Present Invention (See MainlyFIGS. 34 to 41)

In this section, a description will be given to variations of theindividual components forming the devices of the first and thirdsections.

(1) Variations of Column Layout (See Mainly FIGS. 34 to 36).

FIG. 34 is a top view (closer to a real equivalent) of a local portionof the chip which is the cut-away region R1 of the chip corner portioncorresponding to FIG. 3 or 23 for illustrating a variation (asymmetricalstandard arrangement) of the individual components (column layout) inthe semiconductor device of each of the first and second embodiments ofthe present invention. FIG. 35 is a top view (closer to the realequivalent) of the local portion of the chip which is the cut-awayregion R1 of the chip corner portion corresponding to FIG. 3 or 23 forillustrating a variation (asymmetrical trimmed arrangement) of theindividual components (column layout) in the semiconductor device ofeach of the first and second embodiments of the present invention. FIG.36 is a top view (closer to the real equivalent) of the local portion ofthe chip which is the cut-away region R1 of the chip corner portioncorresponding to FIG. 3 or 23 for illustrating a variation (symmetricalL-shaped arrangement) of the individual components (column layout) inthe semiconductor device of each of the first and second embodiments ofthe present invention. Based on these drawings, a description will begiven to variations of the column layout.

FIG. 34 shows an “asymmetrical standard column layout” corresponding tothe column layouts of FIGS. 3 and 23. Here, the wording “asymmetrical”shows that, when a diagonal line 40 of the semiconductor chip or theperipheral corner region is assumed to be a line-symmetry axis, thecolumn layout is not substantially line-symmetrical. As shown in FIG.34, in this example, the peripheral super-junction region basically hasa 3D-Resurf structure. However, into the peripheral corner region 17 b(17 a, 17 c, or 17 d), symmetry in the peripheral side region 16 b hasbeen extended without being lost (having the same symmetry) so that, interms of symmetry around the active-cell-portion super-junctionstructure 14, the layout has low symmetry. In this portion, the layoutno longer has a pure 3D-Resurf structure, and may possibly reduce abreakdown voltage.

To solve the problem, the “asymmetrical trimmed column layout” shown inFIG. 35 has been proposed. In the column layout, the outsides of the Pcolumns 12 p have been trimmed to provide a configuration substantiallymatching the shape of an equi-potential surface (more precisely, a lineof intersection of the equipotential surface and the top surface 1 a ofthe chip 2) in a Blocking Mode. This achieves the effect of improvingmacroscopic symmetry in each of the peripheral corner regions 17 a, 17b, 17 c, and 17 d and reducing the risk of a reduction in breakdownvoltage in this portion.

Thus, in the example of FIG. 35, the macroscopic symmetry can berelatively easily improved. However, the line symmetry has beenimpaired, and the risk of a reduction in breakdown voltage due to theimpaired line symmetry remains.

By contrast, FIG. 36 shows a “symmetrical L-shaped column layout”, inwhich line symmetry with respect to the line-symmetry axis 40 has beengiven to the P columns 12 p in the peripheral corner region 17 b (17 a,17 c, or 17 d) to ensure microscopic symmetry.

These variations can be combined with the example of the first or thirdsection and with each of the following variations of the othercomponents.

(2) Variations of Placement and Shape of P⁻-Type Surface Resurf Region,Relationship Thereof with P Columns, Etc. (See Mainly FIGS. 37 to 39)

FIG. 37 is a top view (closer to the real equivalent) of the localportion of the chip which is the cut-away region R1 of the chip cornerportion corresponding to FIG. 3 or 23 showing a combination of theasymmetrical standard column layout of FIG. 34 and a rectangular P⁻-typesurface resurf region. FIG. 38 is a top view (closer to the realequivalent) of the local portion of the chip which is the cut-awayregion R1 of the chip corner portion corresponding to FIG. 3 or 23showing a combination of the asymmetrical trimmed column layout of FIG.35 and the rectangular P⁻-type surface resurf region. FIG. 39 is a topview (closer to the real equivalent) of the local portion of the chipwhich is the cut-away region R1 of the chip corner portion correspondingto FIG. 3 or 23 showing a combination of the symmetrical L-shaped columnlayout of FIG. 36 and the rectangular P⁻-type surface resurf region.Based on these drawings, a description will be given to variations ofthe placement and shape of the P⁻-type surface resurf region, therelationship thereof with the P columns, and the like.

FIG. 37 shows the variation corresponding to the column layouts of FIGS.3 and 23 (round-corner P⁻-type surface resurf region). As shown in FIG.37, in this variation (right-angled-corner P⁻-type surface resurfregion), the corner of the P⁻-type surface resurf region 8 has a point 8c and is angular (right-angled). The advantage of theright-angled-corner P⁻-type surface resurf region 8 is that a match canbe achieved between the symmetry of the P⁻-type surface resurf region 8in the peripheral corner region 17 b (17 a, 17 c, or 17 d) and thesymmetry (macroscopic symmetry) of the super-junction structure in theperipheral corner region.

Note that the corner point 8 c is preferably over one of the P columns12 p. If the corner point 8 c is over any of the N columns 12 n, a pointof a real PN junction is formed therein to result in the risk ofinducing undesired electric field concentration. However, since the riskis considered to be normally relatively small, the corner point 8 c mayalso be placed over any of the N columns 12 n.

The variation of FIG. 38 is obtained by applying the round-cornerP⁻-type surface resurf region to the asymmetrical trimmed column layoutof FIG. 35. The round-corner P⁻-type surface resurf region isadvantageous in terms of having no corner point, and also has theadvantage of being enhanced in macroscopic symmetry when combined withan asymmetrical trimmed column layout.

The variation of FIG. 39 is obtained by applying the right-angled-cornerP⁻-type surface resurf region to the symmetrical L-shaped column layoutof FIG. 36. The variation is advantageous in that it can achieve a matchbetween the symmetry of the P⁻-type surface resurf region 8 in theperipheral corner region 17 b (17 a, 17 c, or 17 d) and the symmetry(macroscopic symmetry) of the super-junction structure in the peripheralcorner region and also simultaneously satisfy line symmetry with respectto the line-symmetry axis 40.

These variations have been described specifically in this section, butcan be combined with the example of the first or third section and witheach of the variations of the other components in this section.

(3) Variations of Shape, Placement, Etc. of Floating Field Plates (SeeMainly FIGS. 40 and 41)

FIG. 40 is a top view (closer to the real equivalent) of the localportion of the chip which is the cut-away region R1 of the chip cornerportion corresponding to FIG. 3 or 23 for illustrating a variation(right-angle bent corner portion arrangement) of the individualcomponents (layout of floating field plates) in the semiconductor deviceof the second embodiment of the present invention. FIG. 41 is a top view(closer to the real equivalent) of the local portion of the chipcorresponding to the cut-away region R1 of the chip corner portioncorresponding to FIG. 3 or 23 for illustrating a variation (roundlycurved corner portion arrangement) of the individual components (layoutof floating field plates) in the semiconductor device of the secondembodiment of the present invention. Based on these drawings, adescription will be given to variations of the shape, placement, and thelike of the floating field plates.

The “layout of floating field plates with right-angle bent cornerportions” shown in FIG. 40 is an extraction of the layout of thefloating field plates 30 and the like illustrated in FIG. 23. As shownherein, the plan configurations of the floating field plates 30 areglobally rectangles. The corner portions of the floating field plates 30may be right-angled or rounded, but are normally substantiallyline-symmetrical (need not necessary be so, though) with respect to thediagonal line (line-symmetry axis) 40 of the semiconductor chip or theperipheral corner region. Therefore, by achieving a match between thesymmetry of the P⁻-type surface resurf region 8 in the peripheral cornerregion 17 b (17 a, 17 c, or 17 d) and the symmetry of thetwo-dimensional layout of the floating field plates 30 in the peripheralcorner region, it is possible to reduce the risk of an undesiredreduction in breakdown voltage. That is, it is useful to combine thefloating field plate layout of FIG. 40 with the right-angle bent cornerportions with FIG. 37 or FIG. 39.

By also achieving a match between the symmetry (macroscopic symmetry) ofthe super-junction structure in the peripheral corner region 17 b (17 a,17 c, or 17 d) and the symmetry of the two-dimensional layout of thefloating field plates 30 in the peripheral corner region, it is possibleto reduce the risk of an undesired reduction in breakdown voltage. Thatis, it is useful to combine, e.g., the floating field plate layout withthe right-angle bent corner portions of FIG. 40 with FIG. 35 or 36.

The example of FIG. 23 is a combination of the floating field platelayout with the right-angle bent corner portions, the round-cornerP⁻-type surface resurf region, and the asymmetrical standard columnlayout. The macroscopic symmetry of the floating field plate layout andthe column layout is relatively high, but the degree of matching betweenthe macroscopic symmetry thereof and the symmetry in the P⁻-type surfaceresurf region is low.

On the other hand, in a combination of the floating field plate layoutwith the right-angle bent corner portions and FIG. 35, the macroscopicsymmetry of the floating field plate layout and the column layout islow, but the line symmetry thereof is improved.

Next, in a combination of the floating field plate layout with theright-angle bent corner portions and FIG. 36, the macroscopic symmetryof the floating field plate layout and the column layout as well as theline symmetry thereof are improved.

FIG. 41 shows another variation (floating field plate layout withroundly curved corner portions) of the floating field plate layout ofFIG. 40, in which the corner portions of the floating field plates 30having rectangular ring shapes are rounded. Therefore, the layout ofFIG. 41 is particularly preferably combined with the column layout ofFIG. 35 or the P⁻-type surface resurf region 8 of FIG. 38.

These variations that have been specifically described in this sectioncan also be combined with the example of the first or second section andwith each of the variations of the other components in this section.

6. Consideration and Supplemental Description of Each of Embodiments(See Mainly FIGS. 42 to 45)

FIG. 42 is a data plot diagram showing the charge balance ratiodependence of a source/drain breakdown voltage in each of thesemiconductor devices (power MOSFETs each having the super-junctionstructure and a half-width P⁻-type surface resurf region) of each of thefirst and second embodiments of the present invention and asemiconductor device (power MOSFET having a super-junction structure anda full-width P⁻-type surface resurf region) of a comparative example.FIG. 43 is an illustrative view showing a relationship between anelectric field intensity distribution and a peripheral charge amount ina vertical direction (thickness direction of the chip) at the middle ofa P column or the like in a peripheral portion of the chip. FIG. 44 isan illustrative view showing relationship between an electric fieldintensity distribution and a peripheral charge amount in a middleportion of a surface region of the N column or the like in theperipheral portion of the chip. FIG. 45 is an illustrative view forillustrating the principle of an improvement in breakdown voltageresulting from the use of the full-width P⁻-type surface resurf region.Based on these drawings, a supplemental description will be given toevery aspect of the present invention and each of the embodimentsthereof.

(1) Effects of Half-Width P− Surface Resurf Region and Floating FieldPlates on Breakdown Voltage, Etc. (See Mainly FIG. 42)

According to the study conducted by the present inventors, to ensure abreakdown voltage required of a power MOSFET and provide a stabledevice, it is considered to be desirable to design the power MOSFET suchthat, if a breakdown is assumed to occur, the breakdown occurs in atwo-dimensionally wide inner area of an active cell region (reaching themiddle of the depth of a drift region and extending over a relativelywide width). To achieve the desirable design, it is necessary tominimize the possibility of a breakdown in an outer end portion of theactive cell region, i.e., in the vicinity of a P-type main junction orin an edge termination area around a chip.

From this viewpoint, in each of the foregoing embodiments, the 3D-Resurfstructure in which the degree of freedom with which a depletion layerextends is 3 in principle is used in the main area of the peripheralsuper-junction region (edge termination area), while in the active cellregion, the degree of freedom with which the depletion layer extends is2. Therefore, theoretically, a breakdown voltage in the edge terminationarea should be equal to a breakdown voltage in the active cell region.However, it is considered that, in a real device, the breakdown voltagein the edge termination area is about 80% at most of the breakdownvoltage in the active cell region if no measures are taken. Accordingly,even in the peripheral 3D-Resurf structure, the breakdown voltage mayunexpectedly decrease due to local electric field concentration, thelack of charge balance, or the like.

FIG. 42 shows a data plot diagram of the charge balance dependence ofthe source/drain breakdown voltage in each of the power MOSFETs of thefirst embodiment (FIG. 3), the second embodiment (FIG. 23), and thecomparative example (full-width P− surface resurf region). Here, thecircles (o) correspond to FIG. 3, the triangles correspond to FIG. 23,and the squares correspond to a configuration corresponding to FIG. 3 inwhich the entire outer peripheral end of the P⁻-type surface resurfregion has been extended to the vicinity of the outer end portion of theperipheral super-junction region (i.e., comparative example). As can beseen from FIG. 42, in each of the devices of the embodiments, a region(“less perceptible region” where the charge balance dependence of thesource/drain breakdown voltage is less perceptible) is relatively wideon the side on which a charge amount in the P column is larger than acharge amount in the N column. On the other hand, in the comparativeexample, the width of the less perceptible region is relatively narrow.

(2) Description of Relationship Between Breakdown Voltage in EdgeTermination Area and P− Surface Resurf Region, Etc. (See Mainly FIGS. 43and 44)

FIG. 43 schematically shows charge distributions and an electric fieldintensity distribution in a thickness direction in the semiconductorsubstrate of the power MOSFET having the (full-width or half-width) P−surface resurf region of the first embodiment (FIG. 3). In FIG. 43, thecolumnar figure on the left-hand side represents a given unit N columnin the P-surface resurf region, which has been extracted therefrom. Themiddle line of the figure is assumed to be a Z-axis and, on theright-hand side, E(Z), i.e., an electric field intensity distribution inthe thickness direction is shown. Charge distributions Qn and Qpcorresponding to the respective half widths of the unit P column and theunit N column are shown in the middle. In the trench fill method, asshown in FIG. 43 (in the middle thereof), as the position lowers, a heattreatment time in epitaxial growth is longer and a boron concentrationis lower so that the charge distribution Qp in the P column is moresparse as it goes down. Even when a profile is obtained in which theboron concentration in the P column is relatively flat with respect tothe depth direction, due to the tapered trench, the charge distributionQp in the P column is similarly more sparse as it goes down. Therefore,the electric field intensity distribution E(Z) in the depth directionbecomes a relatively ideal one having a peak electric field intensity ata middle depth.

On the other hand, an electric field intensity distribution E(x) alongthe X-axis at the surface of the middle portion of the P column (alongthe longitudinal direction of the P column) in the peripheralsuper-junction region when the P− surface resurf region is thefull-width P-surface resurf region (comparative example) is shown in theupper part of FIG. 44. In addition, the distributions Qp and Qn of thecharge amounts in the P column and the N column adjacent to each otherare also shown. Originally, the P-surface resurf region has beenintroduced so as to avoid the concentration of an electric field on thevicinity of the P-type main junction (end portion of the P body region)by allowing the depletion layer to easily extend along the surface inthe blocking mode. However, in the full-width P-surface resurf region,on the contrary, the electric field tends to be concentrated on thevicinity of the interface between the tip portion of the P− surfaceresurf region and the N-type drift region. This causes a reduction inbreakdown voltage in a chip peripheral portion on the side on which thecharge amount in the P column is larger than the charge amount in the Ncolumn. Accordingly, in each of the embodiments of the presentinvention, the half-width P− surface resurf region is introduced as apreferred example to thereby avoid reduction in breakdown voltage in thevicinity of the channel stop region at the N-type chip edge.

(3) Description of Improvement in Breakdown Voltage Due to Half-Width P−Surface Resurf Region (See Mainly FIG. 45)

A brief description will be given to the reason that reduction inbreakdown voltage in the vicinity of the channel stopper at the chipedge can be avoided by thus introducing the half-width P− surface resurfregion.

FIG. 45 illustrates the mechanism of an improvement in breakdown voltagebased on the principle of superimposition of an electric field or thelike. As a device model corresponding to the first embodiment, the pairof adjacent P column and N column near the lower portion of FIG. 44 andthe vicinities of the both ends thereof are extracted, which can berepresented as the upper figure in the first column of FIG. 45. Thedevice can be decomposed into a simple super-junction structure (thesecond column of FIG. 45) and a concentration gradation structure (thethird column of FIG. 45). The respective electric field intensitydistributions in the first decomposition term and the seconddecomposition term are as shown in the lower figures of the second andthird columns of FIG. 45. A combined electric field intensitydistribution obtained through superimposition thereof is as shown in thelower figure of the first column of FIG. 45. The area of the shadedportion of the combined electric field intensity distributioncorresponds to an improvement in breakdown voltage. That is, in thehalf-width P− surface resurf region, the electric field intensity in thevicinities of the tip portion of the surface resurf region having halfthe width of the full-width P− surface resurf region and the P-type mainjunction increases so that a part of the electric field held in thevicinity of the channel stop region at the N-type chip edge is held inan inner region.

4. Summary

While the invention achieved by the present inventors has beenspecifically described heretofore based on the embodiments thereof, thepresent invention is not limited thereto. It will be appreciated thatvarious changes and modifications can be made in the invention withinthe scope not departing from the gist thereof.

For example, each of the foregoing embodiments has been describedspecifically by using the MOS structure having the planar gate structureas an example, but the present invention is not limited thereto. It willbe appreciated that the present invention is exactly similarlyapplicable to a trench gate structure of a U-MOSFET or the like. Also,as the layout of the gate electrodes of the MOSFET, the example in whichthe gate electrodes are arranged in stripes parallel with the pn columnshas been shown, but the present invention is applicable to variouslayouts in which the gate electrodes are arranged in directionsorthogonal to the pn columns or arranged in a grid-like configuration.

Note that, in each of the foregoing embodiments, the example has beenspecifically described in which the N-channel device is formed mainly inthe upper surface of the N epitaxial layer over the N+ single-crystalsilicon substrate. However, the present invention is not limitedthereto, and a P channel device may also be formed in the upper surfaceof the N epitaxial layer over the P+ single-crystal silicon substrate.

Each of the foregoing embodiments has been described specifically usingthe power MOSFET as an example, but the present invention is not limitedthereto. It will be appreciated that the present invention is alsoapplicable to power devices each having a super-junction structure,i.e., diodes, bipolar transistors (including an IGBT), and the like. Itwill also be appreciated that the present invention is also applicableto semiconductor integrated circuit devices having such power MOSFETs,diodes, bipolar transistors, and the like embedded therein, and soforth.

Also, in each of the foregoing embodiments, the trench fill method hasbeen mainly described specifically as a forming method of thesuper-junction structure, but the present invention is not limitedthereto. It will be appreciated that, e.g., a multi-epitaxial method orthe like can also be used.

In each of the foregoing embodiments, the device formed in thesemiconductor substrate has been mainly described specifically, but thepresent invention is not limited thereto. It will be appreciated thatthe present invention is also applicable substantially without anymodification to devices formed in a GaAs-based semiconductor substrate,a silicon-carbide-based semiconductor substrate, and asilicon-nitride-based semiconductor device.

<Second Part: Portion Mainly Related to 2D-Resurf Structure>

0. Outline of Second Part

In a power-type semiconductor active element such as a power MOSFETwhich is resin-molded, even if it shows an excellent source/drainbreakdown voltage characteristic in a chip state (or in a mounting formother than resin molding), when it is molded with a resin, a breakdownvoltage characteristic may noticeably deteriorate. In a mounting formother than resin molding also, a problem arises that, due to a shift inan amount of interfacial charge over a chip or the like, thesource/drain breakdown voltage characteristic becomes unstable.

According to the result of the study conducted by the present inventors,a Floating Field Ring normally used in Edge Termination and a fieldplate coupled thereto have problems such that constraints on asuper-junction structure and layout increase and an electric fieldreducing means other than a floating field plate is inconvenient to use.

The following is a brief description of the outline of a representativeembodiment of the invention disclosed in the second part.

That is, according to an aspect of the present invention in the secondpart, in a power-type resin-molded semiconductor active element in whicha drift region of a first conductivity type has a super-junctionstructure, the position of a floating field ring provided on the outsideperiphery of an active region is inwardly shifted to be located suchthat, in a main portion, the inner end of the floating field ring isproximate to the inner end of a column of a second conductivity coveredtherewith.

The following is a brief description of an effect obtained according tothe representative embodiment of the invention disclosed in the secondpart.

That is, in a power-type resin-molded semiconductor active element inwhich a drift region of a first conductivity type has a super-junctionstructure, the position of a floating field ring provided on the outsideperiphery of an active region is inwardly shifted to be located suchthat, in a main portion, the inner end of the floating field ring isproximate to the inner end of a column of a second conductivity coveredtherewith. Therefore, the effect of pushing back the extending depletionlayer causes a “Walk-out” phenomenon in the depletion layer, therebyallowing the prevention of the deterioration of the breakdown voltagedue to electric field concentration in an end portion of thesuper-junction structure.

1. Description of Example of Package Structure of Power MOSFET withSuper-Junction Structure, Etc. as Semiconductor Device of EachEmbodiment of Present Invention (See Mainly FIGS. 46 to 48)

Here, to specifically show a package form, a description will be givenby using a TO-3P type as a typical resin-molded package as an example.However, it will be appreciated that a TO-220 type, another resin-moldedpackage, or a package form other than a resin-molded package may also beused.

FIG. 46 is a perspective view of a package of a power MOSFET having asuper-junction structure or the like as a semiconductor device of eachof the embodiments of the present invention. FIG. 47 is a main-portiontop view of the package of FIG. 46 from which a mold resin has beenremoved. FIG. 48 is a cross-sectional view of the package (in a statemolded with the mold resin) corresponding to the B-B′ cross section ofFIG. 47. Based on these drawings, a description will be given to anexample of the package structure of the power MOSFET having thesuper-junction structure or the like as the semiconductor device of eachof the embodiments of the present invention.

As shown in FIGS. 46 to 48, the main body of the package is aresin-molded body 50, from which a header 52 (heat sink) made of, e.g.,a copper-based metal upwardly protrudes. From the lower portion of theresin-molded body 50, a gate terminal G, a drain terminal D, and asource terminal S each also made of a copper-based metal protrude. Asemiconductor chip 2 is die-bonded onto a die pad 53 made of acopper-based metal with a device surface 1 a (first main surface)thereof facing upward. In the upper and lower surfaces of the die pad53, slits 56 are provided. In the header 52 and a boundary portionbetween the header 52 and the die pad 53 (besides, in, e.g., baseportions of outer leads or the like), grooves 55 are provided. The slits56 and the grooves 55 are provided to ensure integrity between theresin-molded body 50 and these metal base materials. In a middle portionof the header 52, circular opening 57 for mounting or the like isprovided. Over the device surface 1 a of the semiconductor chip 2, ametal guard ring 3, a metal source electrode 5, a metal gate electrode7, and the like each formed of an aluminum-based metal or the like areprovided. Between these metal guard ring 3, metal source electrode 5,metal gate electrode 7, and the like and a plurality of wire bondingleads 54, bonding wires 58 such as, e.g., silver wires are coupled. Theresin-molded body 50 is formed by transfer molding or the like using,e.g., a lead frame (examples of a main material thereof includeoxygen-free copper, a copper-tin alloy, a copper-zirconium alloy, andthe like) and a mold resin material (resin tablet). The mold resinmaterial contains, e.g., an epoxy-based resin as a main resin material,a phenol novolac resin as a curing agent, a phosphorus- or amine-basedcompound as a catalyst, fused silica as a filler, a silicone resin as aflexibilizer, an epoxy-based silane compound as a coupling agent,carnauba wax or an ester compound as an internal mold release agent, aflame retardant, a coloring agent, and the like.

2. Description of Device Structure (Peripheral 2D Super-Junction andShifted FFP) of Power MOSFET with Super-Junction Structure, Etc. asExample of Semiconductor Device of First Embodiment of present invention(see mainly FIGS. 49 to 55, 91, and 92)

In this example, a specific description will be given to a planar powerMOSFET formed in a silicon-based semiconductor substrate and having asource/drain breakdown voltage of about 600 volts (with regard to theplanar power MOSFET, the same also holds true in the followingsections). However, it will be appreciated that the present invention isalso applicable to a power MOSFET having another breakdown voltage valueand other devices.

FIG. 49 is a top view of the entire chip (mainly of a surface regionthereof) of the power MOSFET having a super-junction structure as anexample of the semiconductor device according to the first embodiment ofthe present invention. FIG. 50 is a top view of the entire chip (mainlyof an impurity doped structure thereof or the like) of the power MOSFEThaving the super-junction structure as the example of the semiconductordevice according to the first embodiment of the present invention. FIG.51 is a top view of a local portion of the chip corresponding to acut-away region R1 of the chip corner portion of FIG. 49. FIG. 52 is across-sectional view of a local portion of the chip corresponding to theX-X′ cross section of FIG. 51. FIG. 53 is a cross-sectional view of alocal portion of the chip corresponding to the Y-Y′ cross section ofFIG. 51. FIG. 54 is a device schematic cross-sectional view showing apositional relationship between the floating field plates and the Pcolumn regions of FIG. 51. FIG. 55 is a cross-sectional view of a localportion of the chip (corresponding to two active cells) corresponding tothe A-A′ cross section of a cut-away region R2 of the active cellportion of FIG. 49. FIG. 91 is a (first) schematic top view of the chipfor illustrating a structure of the semiconductor device of each of thefirst to third embodiments of the present invention. FIG. 92 is a(second) schematic top view of the chip for illustrating the structureof the semiconductor device of each of the first to third embodiments ofthe present invention. Based on these drawings, a description will begiven to a device structure (peripheral 2D super-junction and shiftedFFP) of the power MOSFET having the super-junction structure or the likeas the example of the semiconductor device of the first embodiment ofthe present invention.

First, a description will be given to a schematic layout of the uppersurface of the chip (typically several millimeters square). As shown inFIG. 49, in the power MOSFET element chip 2 in which the elements areformed over a silicon-based semiconductor substrate (which is a wafer 1before being divided into the individual chips 2) in the form of asquare or rectangular plate, the metal source electrode 5(aluminum-based electrode) located in a center portion occupies a majorarea. Under the metal source electrode 5, an active cell region 4 isprovided, and the outer end portion thereof is a P-type main junction 6(the outer edge portion of a P body region). Inside the P-type mainjunction 6, a repetitive structure portion 4 r of the active cell region4 is provided. Outside the ring-like P-type main junction 6, a P⁻-typesurface resurf region 8 similarly having a ring-like shape and aperipheral super-junction region 9 (region where linear P columns 12 pand an N-type drift region 11 n located therebetween are periodicallyand substantially equidistantly arranged in a peripheral drift region 11or a combined region thereof) are provided. Here, the outer end of theP⁻-type surface resurf region 8 is located in, e.g., the vicinity of anouter end 9 e of the peripheral super-junction region 9.

Further, around the peripheral super-junction region 9, analuminum-based metal guard ring 3 is provided. Between thealuminum-based metal guard ring 3 and the metal source electrode 5, ametal gate electrode 7 for retrieving polysilicon gate electrodes to theoutside is provided. Note that, in FIG. 49 (the same also holds truer inFIGS. 50 and 51), the metal gate electrode 7 is exaggeratingly depictedwider than the real equivalent for easy understanding of a structure ofthe Edge Termination Area.

Next, a description will be given to a two-dimensional diffusionstructure of the chip 2 and a device layout thereof. As shown in FIG.50, in a center portion of the chip 1, the active cell region 4 (underwhich an active-cell-portion super-junction structure 14, i.e., a firstsuper-junction structure exists) is provided. Inside the active cellregion 4, a large number of linear polysilicon gate electrodes 15 areprovided. In addition, outside the ring-like P-type main junction 6which is the outer edge portion of the active cell region 4 andsurrounds the active cell region 4, the ring-like P⁻-type surface resurfregion 8 coupled to the P-type main junction 6 and surrounding theactive cell region 4 is provided.

Next, a description will be given to a super-junction structure aroundthe active-cell-portion super-junction structure 14, i.e., the firstsuper-junction structure, i.e., the peripheral super-junction structure9 (FIG. 49). In peripheral side regions 16 a and 16 c, a secondsuper-junction structure 18 and a third super-junction structure 19 eachof which is coupled to the active-cell-portion super-junction structure14 and has the same orientation as that of the active-cell-portionsuper-junction structure 14 are provided. On the other hand, inperipheral side regions 16 b and 16 d, a fourth super-junction structure21 and a fifth super-junction structure 22 each of which is not coupledto the active-cell-portion super-junction structure 14 and has anorientation orthogonal to that of the active-cell-portion super-junctionstructure 14 are provided. Note that, in the column layout, individualperipheral corner regions 17 a, 17 b, 17 c, and 17 d form periodicextension regions of the peripheral side regions 16 b and 16 d locatedtherebelow or thereabove.

FIG. 51 shows a schematic enlarged view of the portion of FIG. 50corresponding to the cutaway region R1 of the chip corner portion ofFIG. 49 (in which the number of the P columns 12 p is reduced to besmaller than in an actual situation to clearly show the relations amongindividual elements). As shown in FIG. 51, the outer end of the P⁻-typesurface resurf region 8 is located in the vicinity of the outer end 9 eof the peripheral super-junction region 9 around the entire peripherythereof. As shown in FIG. 49, the repetitive structure portion 4 r inthe active cell region is provided with a periodic structure(one-dimensional periodic structure) in which P+ body contact regions 23and the polysilicon gate electrodes 15 alternately repeat. Additionally,in the peripheral super-junction region 9 (FIG. 49), a plurality ofring-like floating field plates 30 (FFPs) are provided so as to surroundthe active cell region 4.

FIG. 52 shows the X-X′ cross section of FIG. 51, while FIG. 53 shows theY-Y′ cross section of FIG. 51. As shown in FIGS. 52 and 53, on thesurface of an N+ drain region 25 (N-type single-crystal siliconsubstrate) of a back surface 1 b of the chip 2, a metal back-surfacedrain electrode 24 is provided. Over the N+ drain region 25, the driftregion 11 is provided and formed of the N columns 12 n, the P columns 12b (P-type drift regions), the N-type drift region 11 n, and the like. Inthe surface area of the drift region 11, the P-type main junction 6 (Pwell, P body region, or the outer edge portion thereof) is provided. Inthe P body region 6, N+ source regions 26, the P+ body contact regions23, and the like are provided. Outside the P-type main junction 6, theP⁻-type surface resurf region 8 is provided to be coupled thereto. Inthe surface area of the N-type drift region 11 n in an end portion ofthe chip 2, an N+ channel stop region 31, a P+ chip peripheral contactregion 32, and the like are provided. Over a semiconductor surfacebetween the pair of N+ source regions 26, the polysilicon gate electrode15 is provided via a gate insulating film 27. Over the polysilicon gateelectrode 15 and a field insulating film 34, an interlayer insulatingfilm 29 is provided. Over the interlayer insulating film 29,aluminum-based electrode films including the metal source electrode 5and the metal guard ring 3 are formed and each electrically coupled tothe N+ drain region 25, the P+ body contact regions 23, the N+ channelstop region 31, the P+ chip peripheral contact region 32, or the like.Note that the width Wn (thickness) of the N column 12 n and the width Wp(thickness) of the P column 12 p are, e.g., about 6 micrometers andabout 4 micrometers (see FIG. 54). The impurity (e.g., phosphorus)concentration of the N column 12 n is, e.g., about 3.3×10¹⁵/cm³, and theimpurity (e.g., boron) concentration of the P column 12 p is, e.g.,about 5.0×10¹⁵/cm³.

FIG. 54 is a main-portion cross-sectional view for illustrating acorrelation between the positions or the like of each of the floatingfield plates 30 shown in FIGS. 51 to 53 and each of the P column regions12 p proximate to or covered by the floating field plates 30 in the mainportion (portion mainly corresponding to the peripheral corner regions17 a, 17 b, 17 c, and 17 d) of the peripheral super-junction region 9(FIG. 49). As shown in FIG. 54, compared with a position 30 s of astandard floating field plate, the position of the floating field plate30 (FFP) mainly used in the present invention is shifted toward theactive cell region 4 by about 20% of the pitch (which is, e.g., about 10micrometers herein) of super-junctions or by about half the width Wp(which is, e.g., about 4 micrometers) of the P column 12 p. This isobvious from a middle line 45 of the P column region 12 p and a middleline 46 of the N column region 12 n in the drawing. Note that, as apreferred example of the width of the floating field plate 30, adimension equal to about half the width of the pitch of thesuper-junctions can be shown. Also, an example of the inner limit (in apreferred range) of the inner end of the floating field plate 30 isshown by an inner end limit 47, while an example of the outer limit (ina preferred range) of the outer end thereof is shown by an outer endlimit 48. In correspondence thereto, a preferred range of the inner endof the floating field plate 30 is shown by a range FI of the inner end,while a preferred range of the outer end thereof is shown by a range FOof the outer end. As a more preferred example in terms of therelationship with the P column region 12 p, a configuration can be shownin which the inner end of the floating field plate 30 and an inner endPCI of the P column region 12 p substantially match, and the outer endof the floating field plate 30 covers an outer end PCO of the P columnregion 12 p and further slightly outwardly extends (by, e.g., about 10%of the pitch of the super-junctions).

On the other hand, FIGS. 91 and 92 show the two-dimensional positions orthe like of the floating field plates and the P column regions (columnregions of second conductivity type) in each of the portions which areshown in FIGS. 52 to 54 more schematically than in FIGS. 50 and 51 (inwhich the number of the P column regions is reduced to be smaller thanin an actual situation to clearly show the mutual relations thereamong).As shown in FIGS. 91 and 92, P column regions 12 pa 1, 12 pa 2, and 12pa 3 and N column regions 12 na 1 and 12 na 2 form a secondsuper-junction structure 18, and P column regions 12 pc 1, 12 pc 2, and12 pc 3 and N column regions 12 nc 1 and 12 nc 2 form a thirdsuper-junction structure 19. On the other hand, P column regions 12 pb1, 12 pb 2, and 12 pb 3 and N column regions 12 nb 1 and 12 nb 2 form afourth super-junction structure 21, and P column regions 12 pd 1, 12 pd2, and 12 pd 3 and N column regions 12 nd 1 and 12 nd 2 form a fifthsuper-junction structure 22. Here, in the example of FIG. 51, thefloating field plates 30 show ring shapes each in the form of arectangular frame along a P column circular region 49 pb (surrounding aninner P column circular region 49 pa and surrounded by an outer P columncircular region 49 pc) formed along a group of the P column regions eachhaving the same ordinal number when counted from the active cell region4 in a radially outward direction, e.g., the P column regions 12 pa 2,12 pb 2, 12 pc 2, and 12 pd 2. However, in the peripheral corner regions17 a, 17 b, 17 c, and 17 d (FIG. 50) (i.e., in the regions other thanthe peripheral main portion including the peripheral side regions 16 a,16 b, 16 c, and 16 d), an equipotential surface when a depletion layerexpands is curved, and therefore the corner portions of the floatingfield plates 30 are not limited to right-angled shapes, and may also becurved, as shown in FIG. 87.

FIG. 55 shows the A-A′ cross section (corresponding to 2 periods of therepetitive structure) of the cutaway region R2 of the active cellportion of FIG. 49. As shown in FIG. 55, on the surface of the N+ drainregion 25 (N-type single-crystal silicon substrate) of the back surface1 b of the chip 2, the metal back-surface drain electrode 24 isprovided. Over the N+ drift region 25, the drift region 11 is providedand formed of the N columns 12 n (N-type drift region 11 n) and the Pcolumns 12 p (P-type drift region 11 p). In the surface area of thedrift region 11, the P body region 6 is provided. In the P body region6, N+ source regions 26, the P+ body contact regions 23, and the likeare provided. Over the semiconductor surface between the pair of N+source regions 26, the polysilicon gate electrode 15 is provided via thegate insulating film 27. Over the polysilicon gate electrode 15, theinterlayer insulating film 29 is provided. Over the interlayerinsulating film 29, the aluminum-based electrode films including themetal source electrode 5 are formed and electrically coupled to the N+drain region 25 and the P+ body contact regions 23.

3. Description of Wafer Process Corresponding to Semiconductor Device ofFirst Embodiment of Present Invention, Etc. (See Mainly FIGS. 56 to 70)

In this section, a process corresponding to the structures of the firstand second sections will be described. However, these process steps arebasically common to other structures so that the following descriptionwill not be repeated in principle for other structures.

FIG. 56 is a wafer cross-sectional view of a device portion shown inFIG. 7 for illustrating a wafer process (step of forming trenches)corresponding to the semiconductor device of the first embodiment of thepresent invention. FIG. 57 is a wafer cross-sectional view of the deviceportion shown in FIG. 52 for illustrating the wafer process (step ofremoving a hard mask for forming the trenches) corresponding to thesemiconductor device of the first embodiment of the present invention.FIG. 58 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of filling the trencheswith a P-type epitaxial layer) corresponding to the semiconductor deviceof the first embodiment of the present invention. FIG. 59 is a wafercross-sectional view of the device portion shown in FIG. 52 forillustrating the wafer process (CMP step) corresponding to thesemiconductor device of the first embodiment of the present invention.FIG. 60 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of introducing aP⁻-type surface resurf region) corresponding to the semiconductor deviceof the first embodiment of the present invention. FIG. 61 is a wafercross-sectional view of the device portion shown in FIG. 52 forillustrating the wafer process (step of patterning a field oxide film)corresponding to the semiconductor device of the first embodiment of thepresent invention. FIG. 62 is a wafer cross-sectional view of the deviceportion shown in FIG. 52 for illustrating the wafer process (step ofintroducing a P body region) corresponding to the semiconductor deviceof the first embodiment of the present invention. FIG. 63 is a wafercross-sectional view of the device portion shown in FIG. 52 forillustrating the wafer process (step of forming a gate insulating film)corresponding to the semiconductor device of the first embodiment of thepresent invention. FIG. 64 is a wafer cross-sectional view of the deviceportion shown in FIG. 52 for illustrating the wafer process (step offorming a gate polysilicon film) corresponding to the semiconductordevice of the first embodiment of the present invention. FIG. 65 is awafer cross-sectional view of the device portion shown in FIG. 52 forillustrating the wafer process (step of patterning the gate polysiliconfilm into gate electrodes) corresponding to the semiconductor device ofthe first embodiment of the present invention. FIG. 66 is a wafercross-sectional view of the device portion shown in FIG. 52 forillustrating the wafer process (step of forming source regions)corresponding to the semiconductor device of the first embodiment of thepresent invention. FIG. 67 is a wafer cross-sectional view of the deviceportion shown in FIG. 52 for illustrating the wafer process (step offorming an interlayer insulating film) corresponding to thesemiconductor device of the first embodiment of the present invention.FIG. 68 is a wafer cross-sectional view of the device portion shown inFIG. 52 for illustrating the wafer process (step of forming contactholes) corresponding to the semiconductor device of the first embodimentof the present invention. FIG. 69 is a wafer cross-sectional view of thedevice portion shown in FIG. 52 for illustrating the wafer process (stepof extending the contact holes and introducing body contact regions)corresponding to the semiconductor device of the first embodiment of thepresent invention. FIG. 70 is a wafer cross-sectional view of the deviceportion shown in FIG. 52 for illustrating the wafer process (step offorming an aluminum-based conductive film) corresponding to thesemiconductor device of the first embodiment of the present invention.Based on these drawings, a description will be given to a wafer processcorresponding to the semiconductor device of the first embodiment of thepresent invention or the like.

First, as shown in FIG. 56, the semiconductor wafer 1 is prepared inwhich, over the N-type single-crystal silicon substrate 25 (which is,e.g., a 200 mm wafer but may also have a wafer diameter of 150 mm, 300mm, or 450 mm) doped with, e.g., antimony (at a concentration of theorder of, e.g., about 10¹⁸/cm³ to 10¹⁹/cm³), a phosphorus-dopedN-epitaxial layer 10 n (drift region at a concentration of the order of,e.g., about 10¹⁵/cm³, which is a portion serving as the N-type driftregion 11 n and also partly serving as the N columns 12 n) having athickness of, e.g., about 45 micrometers is formed. Over a devicesurface 1 a (main surface opposite to the back surface 1 b) of thesemiconductor wafer 1, a hard mask film 33 for forming P-type columntrenches made of, e.g., P-TEOS (Plasma-Tetraethylorthosilicate) or thelike is formed. Next, as shown in FIG. 56, using the hard mask 33 forforming P-type column trenches as a mask, the N epitaxial layer 10 n andthe like are dry-etched to form P-type column trenches 20. Examples of adry etching atmosphere that can be shown include an atmospherecontaining, e.g., Ar, SF₆, O₂, and so forth as main gas components.Examples of the range of the depth of dry etching that can be showninclude a range of, e.g., about 40 to 55 micrometers. Note that theP-type column trenches 20 preferably reach the N-type single-crystalsilicon substrate 25. However, the P-type column trenches 20 need notnecessarily reach the N-type single-crystal silicon substrate 25 as longas they are proximate thereto.

Next, as shown in FIG. 57, the hard mask 33 that is no longer needed isremoved.

Next, as shown in FIG. 58, filling epitaxial growth (in-trench epitaxialfilling method) is performed with respect to the P-type column trenches20 to form a P-type filling epitaxial layer 10 p (dopant is boron at aconcentration of the order of, e.g., about 10¹⁵/cm³). The P-typeepitaxial region 10 p is a portion serving as the P-type drift region 11p and also serving as the P columns 12 p. Examples of conditions for thefilling epitaxial growth that can be shown include a processing pressureof, e.g., about 1.3×10⁴ Pascal to 1.0×10⁵ Pascal, a raw material gas ofsilicon tetrachloride, trichlorosilane, dichlorosilane, monosilane, orthe like.

Next, as shown in FIG. 59, the P-type filling epitaxial layer 10 plocated outside the P-type column trenches 20 is removed by aplanarizing step, e.g., CMP (Chemical Mechanical Polishing), while thesurface 1 a of the semiconductor wafer 1 is simultaneously planarized.Note that, here, a super-junction structure as shown in FIG. 11 may alsobe formed by a multi-epitaxial method besides the trench fill method.

Next, as shown in FIG. 60, the silicon oxide film 34 (field insulatingfilm) is formed by thermal oxidation over substantially the entire topsurface 1 a of the semiconductor wafer 1, and a resist film 35 forintroducing P⁻-type resurf region is formed thereover by lithography.Examples of the thickness of the field insulating film 34 that can beshown include about 350 nm.

Subsequently, using the resist film 35 for introducing P⁻-type resurfregion as a mask, the P⁻-type surface resurf region 8 is introduced byion implantation (of, e.g., boron). Examples of conditions for the ionimplantation that can be shown include an ion species of boron, animplantation energy in a preferred range around, e.g., 200 keV, and adose in a preferred range of, e.g., about 1×10¹¹/cm² to 1×10¹²/cm².Thereafter, the resist film 35 that is no longer needed is removed.

Next, as shown in FIG. 61, over the top surface 1 a of the semiconductorwafer 1, a resist film 36 for etching silicon oxide film is formed bylithography. Subsequently, using the resist film 36 as a mask, the fieldinsulating film 34 is patterned by dry etching using, e.g., afluorocarbon-based etching gas or the like. Thereafter, the resist film36 that is no longer needed is entirely removed.

Next, as shown in FIG. 62, a resist film 37 for introducing P bodyregion is formed over the top surface 1 a of the semiconductor wafer 1by lithography (typically, prior to the formation of the resist film 37,a protective film against ion implantation such as a thermal oxidationfilm of, e.g., about 10 nm is formed over the top surface 1 a of thesemiconductor wafer 1, but a depiction thereof is omitted to preventcomplicated illustration, which is also the same in other portions).Subsequently, using the resist film 37 for introducing P body region asa mask, the P body region 6 is introduced by ion implantation. Examplesof conditions for the ion implantation that can be shown include: (1) anion species of boron, an implantation energy in a preferred rangearound, e.g., 200 keV, and a dose in a preferred range around the orderof, e.g., 10¹³/cm², which are for a first step; and (2) an ion speciesof boron, an implantation energy in a preferred range around, e.g., 75keV, and a dose in a preferred range around the order of, e.g., 10¹²/cm²(a concentration is on the order of, e.g., about 10¹⁷/cm³), which arefor a second step. Thereafter, the resist film 37 that is no longerneeded is entirely removed.

Next, as shown in FIG. 63, over the top surface 1 a of the semiconductorwafer 1, the gate oxide film 27 (gate insulating film) is formed. Anexemplary thickness of the gate insulating film 27 that can be shownranges from, e.g., about 50 nm to 200 nm, though it depends on abreakdown voltage. Examples of a film deposition method that can beshown include a CVD (Chemical Vapor Deposition), a thermal oxidationmethod, and the like. Note that, to wafer cleaning prior to gateoxidation, wet cleaning can be applied which uses, e.g., a firstcleaning solution, i.e., a mixed solution of ammonia, hydrogen peroxide,and pure water at 1:1:5 (volume ratio) and a second cleaning solution,i.e., a mixed solution of hydrochloric acid, hydrogen peroxide, and purewater at 1:1:6 (volume ratio).

Next, as shown in FIG. 64, over the gate oxide film 27, a gate electrodepolysilicon film 15 (having a thickness of, e.g., about 200 nm to 800nm) is formed by, e.g., low-pressure CVD (Chemical Vapor Deposition).

Next, as shown in FIG. 65, the gate electrode polysilicon film 15 ispatterned by dry etching into the gate electrodes 15 and the floatingfield plates 30 (FFPs).

Next, as shown in FIG. 66, a resist film 38 for introducing N+ sourceregions is formed by lithography and, using the resist film 38 as amask, the N+ source regions 26 and the N+ channel stopper region 31 inthe chip edge portion are introduced by ion implantation. Examples ofconditions for the ion implantation that can be shown include an ionspecies of arsenic, an implantation energy in a preferred range around,e.g., 40 keV, and a dose in a preferred range around the order of, e.g.,10¹⁵/cm² (a concentration is on the order of, e.g., about 10²⁰/cm³).Thereafter, the resist film 38 that is no longer needed is entirelyremoved.

Next, as shown in FIG. 67, over substantially the entire surface of thetop surface 1 a of the semiconductor wafer 1, the PSG(Phospho-Silicate-Glass) film 29 (interlayer insulating film) isdeposited by CVD or the like. Note that, as the interlayer insulatingfilm 29, a BPSG film, a TEOS film, a SOG film, a HDP (High DensityPlasma) silicon oxide film, a PSG film, or a laminate film of aplurality of any of the foregoing films may also be used besides the PSGfilm. Preferred examples of the total thickness of the interlayerinsulating film 29 that can be shown include about 900 nm.

Next, as shown in FIG. 68, over the top surface 1 a of the semiconductorwafer 1, a resist film 41 for forming source contact holes is formedand, using the resist film 41 as a mask, source contact holes 39 and thelike are opened by dry etching. Subsequently, the resist film 41 that isno longer needed is entirely removed.

Next, as shown in FIG. 69, the silicon substrate is etched and then, byion implantation, the P+ body contact regions 23 and the P+ chipperipheral contact region 32 are introduced. Examples of conditions forion implantation that can be shown include an ion species of BF₂, animplantation energy in a preferred range around, e.g., 30 keV, and adose in a preferred range around the order of, e.g., 10¹⁵/cm² (aconcentration is on the order of, e.g., about 10¹⁹/cm³).

Next, as shown in FIG. 70, an aluminum-based metal layer is deposited bysputtering or the like via a barrier metal film of TiW or the like andpatterned to form the metal source electrode 5, the guard ring electrode3, and the like.

Then, as necessary, a final passivation film such as, e.g., an inorganicfinal passivation film or an organic-inorganic final passivation film isformed in an upper layer, and pad openings and gate openings are formedtherein. As the final passivation film, a single-layer film such as aninorganic final passivation film or an organic-inorganic finalpassivation film may be formed or, besides, an organic-inorganic finalpassivation film or the like may also be laminated over an under-layerinorganic final passivation film.

Next, a back grinding treatment is performed to reduce the originalwafer thickness (e.g., about 750 micrometers) to, e.g., about 80 to 280micrometers (i.e., a thickness less than 300 micrometers).

In addition, over the back surface 1 b of the wafer 1, the metalback-surface drain electrode 24 (see FIGS. 52, 53, and 55) is depositedby sputtering film deposition. The back-surface metal electrode film 24includes, e.g., a back-surface titanium film (diffusion preventing layerof gold and nickel), a back-surface nickel film (adhesive layer to achip bonding material), a back-surface gold film (oxidation preventinglayer of nickel) which are mentioned in order of increasing distancefrom the wafer 1, and the like. Thereafter, the wafer is divided intoindividual chips, which are subjected to transfer molding using a moldresin or the like, resulting in a packaged device as shown in FIG. 46.

4. Description of Device Structure (Peripheral 2D Super-Junction and NRings) of Power MOSFET with Super-Junction Structure, Etc. as Example ofSemiconductor Device of Second Embodiment of Present Invention (SeeMainly FIGS. 71 to 74 and FIG. 92)

The RESURF structure described herein attains substantially the sameobject as described in the second section. Here, a description will begiven to the case where the resurf structure is used alone, but it willbe appreciated that the resurf structure may also be used incombination. When the resurf structure is used in combination, theeffect thereof is accordingly enhanced.

Note that, structurally, the resurf structure is substantially the sameas described in the second section except that the floating field plates30 have been replaced with N ring regions 42 n (ring regions of firstconductivity type). Therefore, hereinbelow, a description will be givenonly to a different portion in principle.

FIG. 71 is a top view of a local portion of a chip of a power MOSFEThaving a super junction structure as an example of the semiconductordevice of the second embodiment of the present invention correspondingto the cut-away region R1 of the chip corner portion of FIG. 49. FIG. 72is a cross-sectional view of a local portion of the chip correspondingto the X-X′ cross section of FIG. 71. FIG. 73 is a cross-sectional viewof a local portion of the chip corresponding to the Y-Y′ cross sectionof FIG. 71. FIG. 74 is a device schematic cross-sectional view forillustrating a relationship between the N ring regions and P columnregions of FIGS. 72 and 73. Based on these drawings, a description willbe given to a device structure (peripheral 2D super-junction and Nrings) of the power MOSFET having the super-junction structure or thelike as the example of the semiconductor device of the second embodimentof the present invention.

As shown in FIGS. 71 to 74 (see FIG. 92), along the inner end PCI ofeach of the P column circular regions 49 pa, 49 pb, and 49 pc, the Nring region 42 n (ring region of first conductivity type) showing a ringshape in the form of a rectangular frame is provided. However, in theperipheral corner regions 17 a, 17 b, 17 c, and 17 d (FIG. 50) (i.e., inthe regions other than the peripheral main portion including theperipheral side regions 16 a, 16 b, 16 c, and 16 d), an equipotentialsurface when a depletion layer expands is curved, and therefore thecorner portions of the N ring regions 42 n are not limited toright-angled shapes, and may also be curved, as shown in FIG. 89.

The dose or impurity concentration in the N ring region 42 n is higherthan in the N column region 12 n, and is preferably of such a level asto achieve complete depletion in a blocking mode, in the same manner asin the P⁻-type surface resurf region 8. On the other hand, the depth ofthe N ring region 42 n is of the same order as that of, e.g., theP⁻-type surface resurface region 8.

5. Description of Wafer Process Corresponding to Semiconductor Device ofSecond Embodiment of Present Invention, Etc. (See Mainly FIGS. 75 and76)

In this section, a description will be given to a main portion of amanufacturing process for the structure of the fourth section. As awhole, the manufacturing process is substantially the same as describedin the third section. Therefore, hereinbelow, a description will begiven only to a different portion in principle. That is, a differentportion in terms of processing corresponds to FIG. 60.

FIG. 75 is a wafer cross-sectional view of a device portion shown inFIG. 72 for illustrating a wafer process (step of introducing the N ringregions) corresponding to the semiconductor device of the secondembodiment of the present invention. FIG. 76 is a wafer cross-sectionalview of the device portion shown in FIG. 72 for illustrating the waferprocess (step of introducing a P⁻-type surface resurf region)corresponding to the semiconductor device of the second embodiment ofthe present invention. Based on these drawings, a description will begiven to the wafer process corresponding to the semiconductor device ofthe second embodiment of the present invention and the like.

After the processing shown in FIG. 59 is completed, as shown in FIG. 75,a resist film 43 for introducing N rings is formed over substantiallythe entire device main surface 1 a of the wafer 1. Then, by lithographyor the like, the resist film 43 for introducing N rings is patterned.Using the patterned resist film 43 as a mask, the N ring regions 42 n(ring regions of first conductivity type) are introduced by ionimplantation or the like into the surface portions of the drift region11 corresponding to the inner ends of the individual P column regions 12p (column regions of second conductivity type) in the peripheral portion(i.e., edge termination area). Preferred examples of conditions for theion implantation that can be shown include an ion species of phosphorus,an implantation energy of, e.g., about 200 keV, and a dose of, e.g.,about 5×10¹²/cm² (in a preferred range of about 3×10¹²/cm² to7×10¹²/cm²). Thereafter, the resist film 43 that is no longer needed isentirely removed.

Next, as shown in FIG. 76, the silicon oxide film 34 (field insulatingfilm) is formed by, e.g., thermal oxidation over substantially theentire device main surface 1 a of the wafer 1 (examples of the thicknessof the field insulating film 34 that can be shown include about 350 nm),and a resist film 35 for introducing P⁻-type resurf region is formedthereover by lithography. Subsequently, using the resist film 35 forintroducing P⁻-type resurf region as a mask, the P⁻-type surface resurfregion 8 is introduced by ion implantation (of, e.g., boron). Examplesof conditions for the ion implantation that can be shown include an ionspecies of boron, an implantation energy in a preferred range around,e.g., 200 keV, and a dose in a preferred range of, e.g., about1×10¹¹/cm² to 1×10¹²/cm². Thereafter, the resist film 35 that is nolonger needed is removed. After that, the wafer process moves to thestep of FIG. 61, and the process is similarly performed afterward.

6. Description of Device Structure (Peripheral 2D Super-Junction, NRings, and P Rings) of Power MOSFET with Super-Junction Structure, Etc.as Example of Semiconductor Device of Third Embodiment of PresentInvention (See Mainly FIGS. 77 to 80 and 92)

The example of the fourth section is effective in avoiding the influenceof negative movable charges at the interface of a mold resin and arounda passivation film. In this section, a description will be given to aresurf structure (P ring regions 42 p) which is effective in avoidingthe influence of positive movable charges at a similar interface or thelike. Accordingly, if the major type (polarity) of the movable chargesis negative, it may also be possible to use only the N ring regions 42n. Likewise, if the major type of the movable charges is positive, itmay also be possible to use only the P ring regions 42 p describedherein.

The RESURF structure described herein attains substantially the sameobject as described in the second section. Here, a description will begiven to the case where the resurf structure is used alone, but it willbe appreciated that the resurf structure may also be used incombination. When the resurf structure is used in combination, theeffect thereof is accordingly enhanced.

Note that, structurally, the resurf structure is substantially the sameas described in the fourth section. Therefore, a description will begiven herein only to a different portion in principle.

FIG. 77 is a top view of a local portion of a chip of a power MOSFEThaving a super-junction structure as an example of the semiconductordevice of the third embodiment of the present invention corresponding tothe cut-away region R1 of the chip corner portion of FIG. 49. FIG. 78 isa cross-sectional view of a local portion of the chip corresponding tothe X-X′ cross section of FIG. 77. FIG. 79 is a cross-sectional view ofa local portion of the chip corresponding to the Y-Y′ cross section ofFIG. 77. FIG. 80 is a device schematic cross-sectional view forillustrating a relationship between the N ring regions (P ring regions)and P column regions of FIGS. 78 and 79. Based on these drawings, adescription will be given to a device structure (peripheral 2Dsuper-junction, N rings, and P rings) of the power MOSFET with thesuper-junction structure as the example of the semiconductor device ofthe third embodiment of the present invention.

As shown in FIGS. 77 to 80 (see FIG. 92), along the outer end PCO ofeach of the P column circular regions 49 pa, 49 pb, and 49 pc, the Pring region 42 p (ring region of second conductivity type) showing aring shape in the form of a rectangular frame is provided. However, inthe peripheral corner regions 17 a, 17 b, 17 c, and 17 d (FIG. 50)(i.e., in the regions other than the peripheral main portion includingthe peripheral side regions 16 a, 16 b, 16 c, and 16 d), anequipotential surface when a depletion layer expands is curved, andtherefore the corner portions of the P ring regions 42 p are not limitedto right-angled shapes, and may also be curved, as shown in FIG. 89(which shows an example of the N ring region 42 n, but is alsoapplicable to the P ring region 42 p without substantial alteration).

The dose or impurity concentration in the P ring region 42 p is higherthan in the P column region 12 p and the P⁻-type surface resurf region8, and needs to be of such a level as to achieve complete depletion in ablocking mode, in the same manner as in the P⁻-type surface resurfregion 8.

7. Description of Wafer Process Corresponding to Semiconductor Device ofSecond Embodiment of Present Invention, Etc. (See Mainly FIGS. 81 and82)

In this section, a description will be given to a main portion of amanufacturing process for the structure of the sixth section. As awhole, the manufacturing process is substantially the same as describedin the third and fifth sections. Therefore, hereinbelow, a descriptionwill be given only to a different portion in principle. That is, adifferent portion in terms of processing corresponds to FIG. 60. Notethat, if the N ring regions 42 n (ring regions of first conductivitytype) are omitted, the step of FIG. 75 may be skipped appropriately.

FIG. 81 is a wafer cross-sectional view of a device portion shown inFIG. 78 for illustrating a wafer process (step of introducing the P ringregions) corresponding to the semiconductor device of the thirdembodiment of the present invention. FIG. 82 is a wafer cross-sectionalview of the device portion shown in FIG. 78 for illustrating the waferprocess (step of introducing a P⁻-type surface resurf region)corresponding to the semiconductor device of the third embodiment of thepresent invention. Based on these drawings, a description will be givento the wafer process corresponding to the semiconductor device of thesecond embodiment of the present invention and the like.

After the processings shown in FIGS. 59 and 75 are completed, as shownin FIG. 81, a resist film 44 for introducing P rings is formed oversubstantially the entire device main surface 1 a of the wafer 1. Then,by lithography or the like, the resist film 44 for introducing P ringsis patterned. Using the patterned resist film 44 as a mask, the P ringregions 42 p (ring regions of second conductivity type) are introducedby ion implantation or the like into the surface portions of the driftregion 11 corresponding to the outer ends of the individual P columnregions 12 p (column regions of second conductivity type) in theperipheral portion (i.e., edge termination area). Preferred examples ofconditions for the ion implantation that can be shown include an ionspecies of boron, an implantation energy of, e.g., about 200 keV, and adose of, e.g., about 7×10¹²/cm² (in a preferred range of about5×10¹²/cm² to 1×10¹³/cm²). Thereafter, the resist film 44 that is nolonger needed is entirely removed.

Next, as shown in FIG. 82, the silicon oxide film 34 (field insulatingfilm) is formed by, e.g., thermal oxidation over substantially theentire main surface 1 a of the wafer 1 (examples of the thickness of thefield insulating film 34 that can be shown include about 350 nm), and aresist film 35 for introducing P⁻-type resurf region is formed thereoverby lithography. Subsequently, using the resist film 35 for introducingP⁻-type resurf region as a mask, the P⁻-type surface resurf region 8 isintroduced by ion implantation (of, e.g., boron). Examples of conditionsfor the ion implantation that can be shown include an ion species ofboron, an implantation energy in a preferred range around, e.g., 200keV, and a dose in a preferred range of, e.g., about 1×10¹¹/cm² to1×10¹²/cm². Thereafter, the resist film 35 that is no longer needed isremoved. After that, the wafer process moves to the step of FIG. 61, andthe process is similarly performed afterward.

8. Description of Variations of Individual Components in SemiconductorDevices of First to Third Embodiments of Present Invention (See MainlyFIGS. 83 to 90 and Also FIGS. 91 and 92)

In this section, a description will be given to variations of theindividual components forming the devices of the second, fourth, andsixth sections.

(1) Variations of Column Layout (See Mainly FIGS. 83 to 85)

FIG. 83 is a top view (closer to a real equivalent) of the local portionof the chip corresponding to the cut-away region R1 of the chip cornerportion of FIG. 50 for illustrating a variation (asymmetrical standardarrangement) of individual components (column layout) in thesemiconductor device of each of the first to third embodiments of thepresent invention. FIG. 84 is a top view (closer to the real equivalent)of the local portion of the chip corresponding to the cut-away region R1of the chip corner portion of FIG. 50 for illustrating a variation(asymmetrical trimmed arrangement) of the individual components (columnlayout) in the semiconductor device of each of the first to thirdembodiments of the present invention. FIG. 85 is a top view (closer tothe real equivalent) of the local portion of the chip corresponding tothe cut-away region R1 of the chip corner portion of FIG. 50 forillustrating a variation (symmetrical L-shaped arrangement) of theindividual components (column layout) in the semiconductor device ofeach of the first to third embodiments of the present invention. Basedon these drawings, a description will be given to the variations of thecolumn layout.

FIG. 83 shows an “asymmetrical standard column layout” corresponding tothe column layouts of FIGS. 50, 51, 71, and 77. Here, the wording“asymmetrical” shows that, when the diagonal line 40 of thesemiconductor chip or the peripheral corner region is assumed to be aline-symmetry axis, the column layout is not substantiallyline-symmetrical. As shown in FIG. 83, in this example, the peripheralsuper-junction region basically has a 3D-Resurf structure. However, intothe peripheral corner region 17 b (17 a, 17 c, or 17 d), symmetry in theperipheral side region 16 b has been extended without being lost (havingthe same symmetry) so that, in terms of symmetry around theactive-cell-portion super-junction structure 14, the layout has lowsymmetry. In this portion, the layout no longer has a pure 3D-Resurfstructure, and may possibly reduce a breakdown voltage.

To solve the problem, the “asymmetrical trimmed column layout” shown inFIG. 84 has been proposed. In the column layout, the outsides of the Pcolumns 12 p have been trimmed to provide a configuration substantiallymatching the shape of an equi-potential surface (more precisely, a lineof intersection of the equipotential surface and the top surface 1 a ofthe chip 2) in a Blocking Mode. This achieves the effect of improvingmacroscopic symmetry in each of the peripheral corner regions 17 a, 17b, 17 c, and 17 d and reducing the risk of a reduction in breakdownvoltage in this portion.

Thus, in the example of FIG. 84, the macroscopic symmetry can berelatively easily improved. However, the line symmetry has beenimpaired, and the risk of a reduction in breakdown voltage due to theimpaired line symmetry remains.

By contrast, FIG. 85 shows a “symmetrical L-shaped column layout”, inwhich line symmetry with respect to the line-symmetry axis 40 has beengiven to the P columns 12 p in the peripheral corner region 17 b (17 a,17 c, or 17 d) to ensure microscopic symmetry.

These variations can be combined with the example of the second, fourth,or sixth section and with each of the following variations of the othercomponents.

(2) Variations of Layout, Etc. of Floating Field Plates (See MainlyFIGS. 86 and 87)

FIG. 86 is a top view (closer to the real equivalent) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion of FIG. 50 for illustrating a variation (right-angle bentcorner portion arrangement) of the individual components (layout offloating field plates) in the semiconductor device of the firstembodiment of the present invention. FIG. 87 is a top view (closer tothe real equivalent) of the local portion of the chip corresponding tothe cut-away region R1 of the chip corner portion of FIG. 50 forillustrating a variation (roundly curved corner portion arrangement) ofthe individual components (layout of floating field plates) in thesemiconductor device of the first embodiment of the present invention.Based on these drawings, a description will be given to variations ofthe shapes, placement, and the like of the floating field plates.

The “layout of floating field plates with right-angle bent cornerportions” shown in FIG. 86 is an extraction of the layout of thefloating field plates 30 and the like illustrated in FIG. 51. As shownherein, the plan configurations of the floating field plates 30 areglobally rectangles. The corner portions of the floating field platesmay be right-angled or rounded, but are normally substantiallyline-symmetrical (need not necessary be so, though) with respect to thediagonal line (line-symmetry axis) 40 of the semiconductor chip or theperipheral corner region. Therefore, by achieving a match between thesymmetry of the P⁻-type surface resurf region 8 in the peripheral cornerregion 17 b (17 a, 17 c, or 17 d) and the symmetry of thetwo-dimensional layout of the floating field plates 30 in the peripheralcorner region, it is possible to reduce the risk of an undesiredreduction in breakdown voltage. That is, it is useful to combine thefloating field plate layout of FIG. 86 with the right-angle bent cornerportions with FIG. 83 or FIG. 85.

By also achieving a match between the symmetry (macroscopic symmetry) ofthe super-junction structure in the peripheral corner region 17 b (17 a,17 c, or 17 d) and the symmetry of the two-dimensional layout of thefloating field plates 30 in the peripheral corner region, it is possibleto reduce the risk of an undesired reduction in breakdown voltage. Thatis, it is useful to combine, e.g., the floating field plate layout withthe right-angle bent corner portions of FIG. 85 with FIG. 84 or 87.

The example of FIG. 51 is a combination of the floating field platelayout with the right-angle bent corner portions, the round-cornerP⁻-type surface resurf region, and the asymmetrical standard columnlayout. The macroscopic symmetry of the floating field plate layout andthe column layout is relatively high, but the degree of matching betweenthe macroscopic symmetry thereof and the symmetry in the P⁻-type surfaceresurf region is low.

On the other hand, in a combination of the floating field plate layoutwith the right-angle bent corner portions and FIG. 84, the macroscopicsymmetry of the floating field plate layout and the column layout islow, but the line symmetry thereof is improved.

Next, in a combination of the floating field plate layout with theright-angle bent corner portions and FIG. 40, the macroscopic symmetryof the floating field plate layout and the column layout as well as theline symmetry thereof are improved.

FIG. 87 shows another variation (floating field plate layout withroundly curved corner portions) of the floating field plate layout ofFIG. 86, in which the corner portions of the floating field plates 30having rectangular ring shapes are rounded. Therefore, the layout ofFIG. 87 is particularly preferably combined with the column layout ofFIG. 84.

These variations that have been specifically described in this sectioncan also be combined with the example of the second, fourth, or sixthsection and with each of the variations of the other components in thissection.

(3) Layout of N Rings, Etc. (See Mainly FIGS. 88, 89, and 92)

Here, a description will be given only to the N ring regions 42 n (ringregions of first conductivity type), but it will be appreciated that thedescription is also applicable to the P ring regions 42 p (regions ofsecond conductivity type) without substantial alteration.

FIG. 88 is a top view (closer to the real equivalent) of the localportion of the chip corresponding to the cut-away region R1 of the chipcorner portion of FIG. 50 for illustrating a variation (right-angle bentcorner portion arrangement) of the individual components (N ringregions) in the semiconductor device of each of the first to thirdembodiments of the present invention. FIG. 89 is a top view (closer tothe real equivalent) of the local portion of the chip corresponding tothe cut-away region R1 of the chip corner portion of FIG. 50 forillustrating a variation (roundly curved corner portion arrangement) ofthe individual components (N ring regions) in the semiconductor deviceof each of the first to third embodiments of the present invention.Based on these drawings, a description will be given to the layout ofthe N rings and the like.

As shown in FIGS. 71 and 88, the N ring regions 42 n can be formed intorectangular shapes constantly extending along the inner ends PCI of theP column circular regions 49 pa, 49 pb, and 49 pc and having cornerportions bent at right angles, or can also be formed into rectangularshapes having rounded corner portions, as shown in FIG. 89. This isbecause, in the peripheral corner regions 17 a, 17 b, 17 c, and 17 d(FIG. 50), i.e., in the regions other than the peripheral main portionincluding the peripheral side regions 16 a, 16 b, 16 c, and 16 d, anequipotential surface when a depletion layer expands is curved.

These variations that have been specifically described in this sectioncan also be combined with the example of the second, fourth, or sixthsection and with each of the variations of the other components in thissection.

(4) Variations of Cross-Sectional Shapes, Etc. of Floating Field Plates(See Mainly FIG. 90)

FIG. 90 is a device schematic cross-sectional view showing a positionalrelationship between the floating field plates and P column regions eachshown in FIG. 52 or 70 or the like for illustrating a variation(stepped-insulating-film-type FFPs) of the individual components(floating field plates) in the semiconductor device of each of the firstto third embodiments of the present invention. Based on the drawing, adescription will be given to variations of cross-sectional shapes andthe like of the floating field plates.

As shown in FIG. 90, the floating field plates 30 s are basically thesame as the standard floating field plates 30 s shown in FIG. 54 interms of the horizontal positions thereof, but are different therefromin that the main portions thereof located over the P column regions 12 pare formed over the portions of an insulating film 34 t which arerelatively thin compared with the other portion thereof. By thus doingso, the effect of pushing back the extending depletion layer isreinforced, and consequently an effect similar to that achieved by theshifted floating field plates 30 of FIG. 54 can be achieved.

9. Consideration and Supplemental Description of Each of Embodiments(See Mainly FIGS. 93 and 94)

FIG. 93 is a data plot diagram for illustrating the effect of theshifted FFPs of the first embodiment of the present invention. FIG. 94is a data plot diagram for illustrating the effect of the N ring regionsof the second embodiment of the present invention. Based on thesedrawings, a consideration will be given to every aspect of the presentinvention and a supplemental description will be given to each of theembodiments thereof.

(1) Concerning Floating Field Plates (FFPs) (See Mainly FIG. 93)

In regard to FIG. 93, a description will be given first to each ofsamples. “Without FFP” is the sample obtained by removing the floatingfield plates from the chip shown in FIG. 51. “Standard FFP” is thesample corresponding to each of the standard floating field plates 30 sof FIG. 54, which has the inner end thereof located in the vicinity ofthe center of the corresponding P column region 12 p and the outer endthereof located in the vicinity of the center of the corresponding Ncolumn region 12 n. “Half-Width Shifted FFP”, i.e., the floating fieldplate of the first embodiment has the inner end thereof located in thevicinity of the inner end PCI of the corresponding P column region 12 p(which is shifted inward, i.e., toward the active cell region 4 by halfthe width of the P column region 12 p, compared with the standard FFP)and the outer end thereof extending beyond the outer end PCO of the Pcolumn region 12 p and reaching a position slightly outside the P columnregion 12 p. “Full-Width Shifted FFP” is the sample which is shiftedinward, i.e., toward the active cell region 4 by a unit widthcorresponding to the width of the P column region 12 p, compared withthe standard FFP.

The abscissa axis of FIG. 93 shows a surface density of movable chargesat an interface over the device surface 1 a of the semiconductor chip 2or the like. As can be seen from the drawing, in the sample without FFP,the source/drain breakdown voltage has severely deteriorated due to thepresence of a small number of minus movable charges. It can be seenthat, in the sample corresponding to the standard FFP, the point atwhich the source/drain voltage starts to drop is shifted in the negativecharge density range. It can also be seen that, in the samplecorresponding to the half-width shifted FFP, the point at which thesource/drain breakdown voltage starts to drop is horizontally furthershifted in the negative charge density range. However, in the samplecorresponding to the full-width shifted FFP, the source/drain breakdownvoltage does not vary so greatly in the negative charge density range,but the basic source/drain breakdown voltage (around zero charge)significantly drops. This may be conceivably because, due to a reversefield plate effect, electric field concentration has occurred.

Therefore, from the data shown above, it can considered that the innerend of the floating field plate is preferably located in the vicinity ofthe inner end PCI of the P column region 12 p.

Note that, in general, a field plate such as a floating field plate (ora shifted floating field plate also) has the effect of providing ashield against the influence of charge at the interface of a mold resinor passivation film. The inner end portion of the shifted floating fieldplate described in the present application functions as a reverse fieldplate (i.e., pushes back the extending depletion layer). Therefore, itis possible to prevent the deterioration of the source/drain breakdownvoltage due to a Walk-out phenomenon caused in the depletion layer bymovable charges at the interface of the mold resin or passivation film.

(2) Concerning N Ring Regions and P Ring Regions (See Mainly FIG. 94)

A description will be given to each of the samples of FIG. 94. “WithoutN Ring” is the sample which is the same as the sample “Without FFP”,while the other four samples are differentiated by the doses ofphosphorus in the step of FIG. 75. As can be seen from the drawing, inthe sample “without N ring”, the source/drain breakdown voltage hasseverely deteriorated due to the presence of a small number of minusmovable charges. However, it can be seen that, as the dose increases,the point at which the source/drain breakdown voltage starts to dropgradually shifts in the negative charge density range. It can also beseen that, in the range where the dose (of, e.g., phosphorus) is notless than 2×10¹²/cm², especially not less than 3×10¹²/cm², thesource/drain breakdown voltage horizontally extends to a considerablylow negative charge density. Accordingly, the lower limit of the dose ofeach of the N ring regions 42 n can be considered to be about 2×10¹²/cm²or 3×10¹²/cm². As for the upper limit thereof, it needs to be lower thanan upper limit concentration at which complete depletion occurs, andtherefore the upper limit of the dose of the N ring region 42 n can beconsidered to be about 7×10¹²/cm².

The lower limit of the dose (of, e.g., boron) of each of the P ringregions 42 p can also be considered to be about 3×10¹²/cm² or5×10¹²/cm². As for the upper limit thereof, it needs to be lower than anupper limit concentration at which complete depletion occurs, andtherefore the upper limit of the dose of the P ring region 42 p can beconsidered to be about 1×10¹³/cm².

Each of the N ring regions inhibits a hole inversion layer from beingformed in the surface of the N column in the presence ofnegative-polarity movable charges at the interface of a resin orpassivation film and enables the negative-polarity movable charges topass through an equipotential surface in the region to thereby ensurethe voltage supporting ability of each of the N columns. On the otherhand, each of the P ring regions inhibits an electron accumulation layerfrom being formed in the surface of the N column in the presence ofpositive-polarity movable charges at the interface of a resin orpassivation film to ensure the voltage supporting ability in the region.

10. Summary

While the invention achieved by the present inventors has beenspecifically described heretofore based on the embodiments thereof, thepresent invention is not limited thereto. It will be appreciated thatvarious changes and modifications can be made in the invention withinthe scope not departing from the gist thereof.

For example, each of the foregoing embodiments has been describedspecifically by using the MOS structure having the planar gate structureas an example, but the present invention is not limited thereto. It willbe appreciated that the present invention is exactly similarlyapplicable to a trench gate structure of a U-MOSFET or the like. Also,as the layout of the gate electrodes of the MOSFET, the example in whichthe gate electrodes are arranged in stripes parallel with the pn columnshas been shown, but the present invention is applicable to variouslayouts in which the gate electrodes are arranged in directionsorthogonal to the pn columns or arranged in a grid-like configuration.

Note that, in each of the foregoing embodiments, the example has beenspecifically described in which the N-channel device is formed mainly inthe upper surface of the N epitaxial layer over the N+ single-crystalsilicon substrate. However, the present invention is not limitedthereto, and a P channel device may also be formed in the upper surfaceof the N epitaxial layer over the P+ single-crystal silicon substrate.

Each of the foregoing embodiments has been described specifically usingthe power MOSFET as an example, but the present invention is not limitedthereto. It will be appreciated that the present invention is alsoapplicable to power devices each having a super-junction structure,i.e., diodes, bipolar transistors (including an IGBT), and the like. Itwill also be appreciated that the present invention is also applicableto semiconductor integrated circuits having such power MOSFETs, diodes,bipolar transistors, and the like embedded therein, and so forth.

Also, in each of the foregoing embodiments, the trench fill method hasbeen mainly described specifically as a forming method of thesuper-junction structure, but the present invention is not limitedthereto. It will be appreciated that, e.g., a multi-epitaxial method orthe like can also be used.

In each of the foregoing embodiments, the device formed in thesemiconductor substrate has been mainly described specifically, but thepresent invention is not limited thereto. It will be appreciated thatthe present invention is also applicable substantially without anymodification to devices formed in a GaAs-based semiconductor substrate,a silicon-carbide-based semiconductor substrate, and asilicon-nitride-based semiconductor device.

<Third Part: Portion Mainly Concerning Local Charge Balance>

0. Outline of Third Part

The present inventors have produced various power-type active elementssuch as a power MISFET (or power MOSFET) having a super-junctionstructure and performed simulation with regard thereto to study layoutswhich can constantly ensure a required breakdown voltage (such assource/drain breakdown voltage). As a result, with regard to an activecell portion or the like, an almost satisfactory super-junctionstructure has been able to be configured. However, it has become clearthat electric field concentration is likely to occur in a chipperipheral portion and a breakdown has occurred in a region where chargebalance is lost. That is, according to the result of the study conductedby the present inventors, in, e.g., a 2D peripheral resurf structure,charge balance is lost (loss of charge symmetry) in a gap between pairsof P columns extending from the left and right sides of corner portion,connecting portions therebetween (bent portions formed thereby), or thelike. As a result, electric field concentration occurs in the peripheryof the portion in question to result in a drop in breakdown voltage.

The following is a brief description of the outline of a representativeembodiment of the invention disclosed in the present part.

That is, according to an aspect of the present invention in the presentpart, in a power MOSFET having a super-junction structure, thesuper-junction structure (i.e., corner-portion super-junction structure)in a corner portion of a semiconductor chip is laid out so as tomaintain local charge balance.

The following is a brief description of an effect obtained according tothe representative embodiment of the invention disclosed in the presentpart.

That is, in a power MOSFET having a super-junction structure, thesuper-junction structure in a corner portion of the semiconductor chipis laid out so as to maintain local charge balance. Therefore, it ispossible to avoid undesired electric field concentration resulting fromcharge imbalance in the chip corner portion.

1. Description of Charge-Balanced-Type 2D Peripheral Resurf Structure,Etc. in Semiconductor Device of First Embodiment of Present Invention(See Mainly FIGS. 95 and 97)

The example of the second part relates to the non-charge-balanced-type2D peripheral resurf structure (with the floating field plates), whilethe example of this section relates to a charge-balanced-type 2Dperipheral resurf structure (without the floating field plates)corresponding to a charge-balanced version thereof. Accordingly, e.g., apackage and the like are described in detail in the first section of thesecond part, a chip structure other than a P column layout in a chipcorner portion and the like are described in detail in the second,fourth, sixth, and like sections of the second part, a processassociated therewith is described in detail in the third, fifth,seventh, and like sections of the second part, and variations thereofand the like are described in detail in the eighth and like sections ofthe second part. Therefore, hereinbelow, a description will be givenonly to a different portion in principle.

Note that, in the third part, a specific description will be given tothe case where a thickness Wn of an N column and a thickness Wp of a Pcolumn are different (i.e., the impurity concentrations of the tworegions are different). However, it will be appreciated that thethickness Wn of the N column and the thickness Wp of the P column may beset substantially equal (i.e., the impurity concentrations of the tworegions are substantially equal).

FIG. 95 is a top view of a cut-away region R1 of a chip corner portionfor illustrating a charge-balanced-type 2D peripheral resurf structurein a semiconductor device of a first embodiment of a third part of thepresent invention. FIG. 96 is a schematic top view of the chip cornerportion corresponding to FIG. 95. FIG. 97 is a locally enlarged view(for easier understanding of a charge balancing treatment, the width ofeach of N columns is reduced to provide an equal area when charge isbalanced) corresponding to a partially cut-away region R3 of the cornerportion of FIG. 96 subjected to the charge balancing treatment. Based onthese drawings, a description will be given to a charge-balanced-type 2Dperipheral resurf structure and the like in the semiconductor device ofthe first embodiment of the present invention.

For example, in a non-charge-balanced-type corner column layout as shownin FIG. 83 or 85 also, in the active-cell-portion super-junctionstructure 14 and the peripheral side regions 16 a and 16 b (16 c and 16d), one-dimensional periodicity is held so that charge balance isrelatively easy to hold. On the other hand, in the peripheral cornerregion 17 b (17 a, 17 c, or 17 d), two-dimensional layout is performedand, e.g., the P column regions 12 p extending from the two sides comeinto proximity to each other in slightly spaced-apart relation or form abent portion in the vicinity of the connection point therebetween (e.g.,a layout substantially symmetrical with respect to a diagonal line asshown in FIG. 85, i.e., a quasi-symmetrical type). In another case, thesuper-junction structure is extended with the same symmetry from oneside (e.g., an asymmetrical layout with respect to a diagonal line, asshown in FIG. 83, i.e., an asymmetrical type). As a result, in anasymmetrical non-charge-balanced-type corner column layout, the symmetryof a depletion layer is different from the symmetry of the column layoutin the corner portion, and local charge imbalance tends to be induced bythe difference. On the other hand, in a quasi-symmetricalnon-charge-balanced-type corner column layout, the relationship with thesymmetry of the depletion layer in the corner portion has beenrelatively improved but, around the portion where the P column regionsare disconnected or form the bent portion, local charge imbalance tendsto be induced. By contrast, the example of the present section is basedon the quasi-symmetrical non-charge-balanced-type corner column layout,and performs a local charge balancing treatment around the portion wherethe P column regions are disconnected or form the bent portion.

FIG. 95 shows a P column layout in the charge-balanced-type chip cornerportion. As shown in FIG. 95, the column layout is the same as thenon-charge-balanced-type column layout in the active-cell-portionsuper-junction structure 14 and the peripheral side region 16 a or 16 b(16 c or 16 d). However, in the peripheral corner region 17 b (17 a, 17c, or 17 d), compared with the non-charge-balanced-type bent layout(FIG. 85), the P column regions 12 p are disconnected in a portion alonga diagonal line 40. Also, the respective end portions of the individualP column regions 12 p extending from the two sides are in mutuallyinterengaged positional relation.

For easier understanding of the relation, FIG. 96 schematically shows areduced number of the P column regions 12 p. To describe the mutualrelationship between the P column regions 12 p extending in the X- andY-directions, a partially cut-away region R3 in the corner portionsubjected to the charge balancing treatment is enlargedly deformed andshown in FIG. 97. In FIG. 97, the thickness Wn of each of the N columnsis displayed in reduced relation (“N column reduced display”) such thatthe thickness Wn of the N column and the thickness Wp of each of the Pcolumns are substantially the same in the drawing (only in this drawing,Wn=Wp is apparently satisfied). Accordingly, the amount of chargeincluded in the same area is equal. As shown in FIG. 97, in thecharge-balanced-type corner column layout, the respective amounts ofcharge in the similarly hatched half-width regions (belt-like regionshaving the widths Wn/2 and Wp/2 each corresponding to half the thicknessof the column) on both sides of the longitudinal side of the P columnregion 12 p have the same absolute value and the opposite signs.Therefore, if the hatched portions are laid out in such an amount as tooccupy the entire region (e.g., the peripheral corner region 17 b),local charge balance is consequently held. It will be understood that,for this purpose, the middle of the shorter side of the P column region12 p may be located appropriately on the diagonal line 40 of thesemiconductor chip or the peripheral corner region and the mostproximate distance between the proximate P column regions 12 p may beset appropriately to about one-half Wn/2 of the thickness of the Ncolumn.

Note that, as shown in FIG. 96 or the like, it is desirable that thecorner-portion super-junction structure does not contain a micro-column,i.e., a minute P column region 12 p. This is because, if a micro-columnexists, when filling is performed according to a trench epitaxialfilling method, the micro-column has a filling property different fromthose of the other macroscopic P column regions 12 p, and consequently aprocess window which allows the filling property to be excellentlyretained is reduced. Here, the “micro-column” refers to the P columnregion 12 p having a length which is less than double the width orthickness Wp thereof. Also, the “macroscopic column” refers to the Pcolumn region 12 p having a length which is not less than double thewidth or thickness Wp thereof.

2. Description of Charge-Balanced-Type 3D Peripheral Resurf Structure,Etc. in Semiconductor Device of Second Embodiment of Present Invention(See Mainly FIGS. 98 to 100)

The example of the first part relates to the non-charge-balanced-type 3Dperipheral resurf structure (with the half-width P⁻-type surface resurfregion), while the example of this section relates to acharge-balanced-type 3D peripheral resurf structure (without thehalf-width P⁻-type surface resurf region) corresponding to acharge-balanced version thereof. Accordingly, e.g., a chip structureother than a P column layout in a chip corner portion and the like aredescribed in detail in the first, third, and like sections of the firstpart, a process associated therewith is described in detail in thesecond, fourth, and like sections of the first part, and variationsthereof and the like are described in detail in the fifth and likesections of the first part. Therefore, hereinbelow, a description willbe given only to a different portion in principle.

Note that, e.g., the package and the like are substantially the same asdescribed in the first section of the second part.

FIG. 98 is a top view of the cut-away region R1 of the chip cornerportion for illustrating a charge-balanced-type 3D peripheral resurfstructure in a semiconductor device of a second embodiment of the thirdpart of the present invention. FIG. 99 is a schematic top view of thechip corner portion corresponding to FIG. 98. FIG. 100 is a locallyenlarged view (for easier understanding of the charge balancingtreatment, the width of each of the N columns is reduced to provide anequal area when charge is balanced, i.e., “N column reduced display” isperformed) corresponding to the partially cut-away region R3 of thecorner portion of FIG. 99 subjected to the charge balancing treatment.Based on these drawings, description will be given to acharge-balanced-type 3D peripheral resurf structure and the like in thesemiconductor device of the second embodiment of the present invention.

For example, in a non-charge-balanced-type corner column layout as shownin FIG. 34 or 36 also, in the active cell portion super-junctionstructure 14 and the peripheral side regions 16 a and 16 b (16 c and 16d), one-dimensional periodicity is held so that charge balance isrelatively easy to hold. On the other hand, in the peripheral cornerregion 17 b (17 a, 17 c, or 17 d), two-dimensional layout is performedand, e.g., the L-shaped P column regions 12 p are repeatedly arranged tobe substantially symmetrical with respect to the diagonal line (e.g., aquasi-symmetrical type as shown in FIG. 36). Alternatively, thesuper-junction structure is extended with the same symmetry from oneside (e.g., an asymmetrical layout with respect to a diagonal line, asshown in FIG. 34, i.e., an asymmetrical type). As a result, in anasymmetrical non-charge-balanced-type corner column layout, the symmetryof a depletion layer is different from the symmetry of the column layoutin the corner portion, and a local charge imbalance tends to be inducedby the difference. On the other hand, in a quasi-symmetricalnon-charge-balanced-type corner column layout, the relationship with thesymmetry of the depletion layer in the corner portion has beenrelatively improved but, around the portion where the P column regionsare disconnected or form the bent portion, local charge imbalance tendsto be induced. By contrast, the example of the present section is basedon the quasi-symmetrical non-charge-balanced-type corner column layout,and performs a local charge balancing treatment around the portion wherethe P column regions are disconnected or form the bent portion.

FIG. 98 shows a P column layout in the charge-balanced-type chip cornerportion. As shown in FIG. 98, the column layout is the same as thenon-charge-balanced-type column layout in the active-cell-portionsuper-junction structure 14 and the peripheral side region 16 a or 16 b(16 c or 16 d). However, in the peripheral corner region 17 b (17 a, 17c, or 17 d), compared with the non-charge-balanced-type bent layout(FIG. 36), the P column regions 12 p are disconnected in a portion alonga diagonal line 40. Also, the respective end portions of the individualP column regions 12 p extending from the two sides are in mutuallyinterlocking positional relation.

For easier understanding of the relation, FIG. 99 schematically shows areduced number of the P column regions 12 p. To describe the mutualrelationship between the P column regions 12 p extending in the X- andY-directions, a partially cut-away region R3 in the corner portionsubjected to the charge balancing treatment is enlargedly deformed andshown in FIG. 100. In FIG. 100, the thickness Wn of each of the Ncolumns is displayed in reduced relation (“N column reduced display”)such that the thickness Wn of the N column and the thickness Wp of eachof the P columns are substantially the same in the drawing (only in thisdrawing, Wn=Wp is apparently satisfied). Accordingly, the amount ofcharge included in the same area is equal. As shown in FIG. 100, in thecharge-balanced-type corner column layout, the respective amounts ofcharge in the similarly hatched half-width regions (belt-like regionshaving the widths Wn/2 and Wp/2 each corresponding to half the thicknessof the column) on both sides of the longitudinal side of the P columnregion 12 p have the same absolute value and the opposite signs.Therefore, if the hatched portions are laid out in such an amount as tooccupy the entire region (e.g., the peripheral corner region 17 b),local charge balance is consequently held. It will be understood that,for this purpose, the middle of the shorter side of the P column region12 p may be located appropriately on the diagonal line 40 of thesemiconductor chip or the peripheral corner region and the mostproximate distance between the proximate P column regions 12 p may beset appropriately to about one-half Wn/2 of the thickness of the Ncolumn.

3. Description of First Variation of Above Second Embodiment (3DPeripheral Resurf Structure and Half-Width Surface Resurf Layer) (SeeMainly FIG. 101)

The example of the section is obtained by using a half-width P⁻-typesurface resurf region, in place of the full-width P⁻-type surface resurfregion, in the example descried in the second section. As for thehalf-width P⁻-type surface resurf region, it is described in detail inthe first part so that the description thereof is not repeated herein.

FIG. 101 is a schematic top view of a chip corner portion forillustrating a first variation (3D peripheral resurf structure andhalf-width surface resurf layer) of the second embodiment of the thirdpart of the present invention. Based on the drawing, a description willbe given to a first variation (3D peripheral resurf structure andhalf-width surface resurf layer) of the second embodiment describedabove.

As shown in FIG. 101, the layout of the P column regions 12 p in theperipheral corner region 17 b (17 a, 17 c, or 17 d) is ofcharge-balanced type, and the half-width P⁻-type surface resurf region 8is used.

4. Description of Second Variation of Each of Above First and SecondEmbodiments (Trimming of Super-Junction Corner Portion) (See MainlyFIGS. 102 and 103)

The example of this section relates to trimming of the corner of thecharge-balanced-type 2D peripheral resurf structure of the second partcorresponding to FIG. 84 and trimming of the corner of thecharge-balanced-type 3D peripheral resurf structure of the first partcorresponding to FIG. 35.

FIG. 102 is a top view of the cut-away region R1 of a chip cornerportion for illustrating a charge-balanced-type 2D peripheral resurfstructure in a second variation (trimming of a super-junction cornerportion) of the first embodiment of the third part of the presentinvention. FIG. 103 is a top view of the cut-away region R1 of a chipcorner portion for illustrating a charge-balanced-type 3D peripheralresurf structure in a second variation (trimming of the super-junctioncorner portion) of the second embodiment of the third part of thepresent invention. Based on these drawings, a description will be givento a second variation (trimming of super-junction corner portions) ofeach of the first and second embodiments described above.

(1) Trimming of Corners of Charge-Balanced-Type 2D Peripheral ResurfStructure (See Mainly FIG. 102)

A charge-balanced-type 2D peripheral resurf structure as shown in FIG.95 has a relatively excellent relationship with the symmetry of adepletion layer in a chip corner portion. However, the shape of theenvelope of an extended portion of the P column region 12 p is differentfrom the shape of an equipotential line in the depletion layer and, inthat portion, charge balance may be lost. To prevent this, as shown inFIG. 102, a trimming treatment is performed here with respect to theextended portion of the P column region 12 p of FIG. 95 in accordancewith the shape of the equipotential line in the depletion layer in thechip surface.

(2) Trimming of Corners of Charge-Balanced-Type 3D Peripheral ResurfStructure (See Mainly FIG. 103)

A charge-balanced-type 3D peripheral resurf structure as shown in FIG.98 has a relatively excellent relationship with the symmetry of adepletion layer in a chip corner portion. However, the shape of theenvelope of an extended portion of the P column region 12 p is differentfrom the shape of an equipotential line in the depletion layer and, inthat point, charge balance may be lost. To prevent this, as shown inFIG. 103, a trimming treatment is performed here with respect to theextended portion of the P column region 12 p of FIG. 98 in accordancewith the shape of the equipotential line in the depletion layer in thechip surface.

5. Description of Third Variation of Each of Above First and SecondEmbodiments (Combination with Floating Field Plates) (See Mainly FIGS.104 and 105)

The example of this section relates to the application of floating fieldplates to the charge-balanced-type 2D peripheral resurf structurecorresponding to the second section of the second part and theapplication of floating field plates to the charge-balanced-type 3Dperipheral resurf structure corresponding to the third section of thefirst part.

FIG. 104 is a schematic top view of a chip corner portion forillustrating a third variation (combination with floating field plates)of the first embodiment of the third part of the present invention. FIG.105 is a schematic top view of a chip corner portion for illustrating athird variation (combination with floating field plates) of the secondembodiment of the third part of the present invention. Based on thesedrawings, a description will be given to a third variation (combinationwith the floating field plates) of each of the first and secondembodiments described above.

(1) Application of FFPs to Charge-Balanced-Type 2D Peripheral ResurfStructure (See Mainly FIG. 104)

As shown in FIG. 104, this example is obtained by applying thecharge-balanced-type P column region layout in the chip corner portionof FIG. 95 to the 2D peripheral resurf structure having the full-widthP⁻-type surface region 8 and the floating field plates 30 described inthe second section of the second part.

(2) Application of FFPs to Charge-Balanced-Type 3D Peripheral ResurfStructure (See Mainly FIG. 105)

As shown in FIG. 105, this example is obtained by applying thecharge-balanced-type P column region layout in the chip corner portionof FIG. 98 and the floating field plates 30 (the application of thefloating field plates 30 is obviously arbitrary) to the 3D peripheralresurf structure having the half-width P⁻-type surface region 8described in the first section of the first part.

6. Description of Fourth Variation of Above First Embodiment(Combination with N Rings or P Rings) (See Mainly FIG. 106)

The example of the fourth or sixth section of the second part relatesthe non-charge-balanced-type 2D peripheral resurf structure, while theexample of this section relates to the charge-balanced-type 2Dperipheral resurf structure corresponding to the charge-balanced versionthereof. Accordingly, e.g., a package and the like are described indetail in the first section of the second part, a chip structure otherthan a P column layout in a chip corner portion and the like aredescribed in detail in the fourth, sixth, and like sections of thesecond part, a process associated therewith is described in detail inthe fifth, seventh, and like sections of the second part, and variationsthereof and the like are described in detail in the eighth and likesections of the second part. Therefore, hereinbelow, a description willbe given only to a different portion in principle.

Note that, here, a description will be given to an example having both Nring regions and P ring regions but, obviously, it is sufficient if atleast one of the N ring regions and the P ring regions is provided.

FIG. 106 is a schematic top view of a chip corner portion forillustrating a fourth variation (combination with N rings or P rings) ofthe first embodiment of the third part of the present invention. Basedon the drawing, a description will be given to a fourth variation(combination with the N rings or P rings) of the first embodimentdescribed above.

As shown in FIG. 106, the example of this section is obtained byapplying the charge-balanced-type P column region layout in the chipcorner portion illustrated in FIG. 95 to the 2D peripheral resurfstructure having the N ring regions 42 n and the P ring regions 42 p ofthe sixth section of the second part. Note that, to the resultingstructure, floating field plates as described in the article (1) of thefifth section may further be applied.

7. Consideration and Supplemental Description of Each of Embodiments(See Mainly FIGS. 107 to 109)

FIG. 107 is a data plot diagram (including the result of simulation in acell portion) showing a relationship between charge balance andbreakdown voltage in a non-charge-balanced-type 2D peripheral resurfstructure. FIG. 108 is a data plot diagram (including the result ofsimulation in a cell portion) showing a relationship between chargebalance and breakdown voltage in a non-charge-balanced-type 3Dperipheral resurf structure. FIG. 109 is a data plot diagram (includingthe result of simulation in a cell portion) showing a relationshipbetween charge balance and breakdown voltage in each of various 2Dperipheral resurf structures. Based on these drawings, a considerationand a supplemental description will be given to each of the embodimentsthereof.

In FIG. 107, the solid line with no dot represents the result ofsimulation in an active cell portion (i.e., calculated values for thecell portion) as reference data, and data shown by the black squaresrepresents the charge imbalance ratio dependence of the breakdownvoltage of the portion in question in a typical 2D peripheral resurfstructure (i.e., a 2D non-balanced type) as shown in, e.g., FIG. 50.From the drawing, it will be understood that, in the typical 2Dperipheral resurf structure, there is a significant drop in breakdownvoltage particularly in the corner portion when the charge amount Qp inthe P column is excessive.

In FIG. 108, the solid line with no dot represents the result ofsimulation in an active cell portion (i.e., calculated values for thecell portion) as reference data, and data shown by the black squaresrepresents the charge imbalance ratio dependence of the breakdownvoltage of the portion in question in a typical 3D peripheral resurfstructure (i.e., a 3D non-balanced type) as shown in, e.g., FIG. 2. Fromthe drawing, it will be understood that, in the typical 3D peripheralresurf structure, there is a significant drop in breakdown voltageparticularly in the corner portion when the charge amount Qn in the Ncolumn is excessive, though it is not so significant as in the 2Dperipheral resurf structure.

In FIG. 109, the solid line with no dot represents the result ofsimulation in an active cell portion (i.e., calculated values for thecell portion) as reference data, and data shown by the black squaresrepresents the charge imbalance ratio dependence of the breakdownvoltage of the portion in question in a typical 2D peripheral resurfstructure (i.e., a 2D non-balanced type) as shown in, e.g., FIG. 50. Onthe other hand, data shown by the white squares represents the chargeimbalance ratio dependence of the breakdown voltage of the portion inquestion in a charge-balanced-type 2D peripheral resurf structure (i.e.,a 2D balanced type) as shown in, e.g., FIG. 96, while data shown by theblack triangles represents the charge imbalance ratio dependence of thebreakdown voltage of the portion in question in a charge-balanced-type2D peripheral resurf structure having floating field plates (FFPs)(i.e., a 2D balanced type with FFPs) as shown in, e.g., FIG. 104. Fromthe drawings, it will be understood that, in each of the 2D peripheralresurf structures of the 2D balanced type and the 2D balance typed withFFPs, the deterioration of the breakdown voltage when the charge amountQp in the P column is excessive has been considerably improved.

8. Summary

While the invention achieved by the present inventors has beenspecifically described heretofore based on the embodiments thereof, thepresent invention is not limited thereto. It will be appreciated thatvarious changes and modifications can be made in the invention withinthe scope not departing from the gist thereof.

For example, each of the foregoing embodiments has been describedspecifically by using the MOS structure having the planar gate structureas an example, but the present invention is not limited thereto. It willbe appreciated that the present invention is exactly similarlyapplicable to a trench gate structure of a U-MOSFET or the like. Also,as the layout of the gate electrodes of the MOSFET, the example in whichthe gate electrodes are arranged in stripes parallel with the pn columnshas been shown, but the present invention is applicable to variouslayouts in which the gate electrodes are arranged in directionsorthogonal to the pn columns or arranged in a grid-like configuration.

Note that, in each of the foregoing embodiments, the example has beenspecifically described in which the N-channel device is formed mainly inthe upper surface of the N epitaxial layer over the N+ single-crystalsilicon substrate. However, the present invention is not limitedthereto, and a P channel device may also be formed in the upper surfaceof the N epitaxial layer over the P+ single-crystal silicon substrate.

Each of the foregoing embodiments has been described specifically usingthe power MOSFET as an example, but the present invention is not limitedthereto. It will be appreciated that the present invention is alsoapplicable to power devices each having a super-junction structure,i.e., diodes, bipolar transistors (including an IGBT), and the like. Itwill also be appreciated that the present invention is also applicableto semiconductor integrated circuit devices having such power MOSFETs,diodes, bipolar transistors, and the like embedded therein, and soforth.

Also, in each of the foregoing embodiments, the trench fill method hasbeen mainly described specifically as a forming method of thesuper-junction structure, but the present invention is not limitedthereto. It will be appreciated that, e.g., a multi-epitaxial method orthe like can also be used.

In each of the foregoing embodiments, the device formed in thesemiconductor substrate has been mainly described specifically, but thepresent invention is not limited thereto. It will be appreciated thatthe present invention is also applicable substantially without anymodification to devices formed in a GaAs-based semiconductor substrate,a silicon-carbide-based semiconductor substrate, and asilicon-nitride-based semiconductor device.

What is claimed is:
 1. A semiconductor device, comprising: (a) asemiconductor chip having a first main surface provided with a sourceelectrode of a power MOSFET and a second main surface provided with adrain electrode of the power MOSFET; (b) a drift region of a firstconductivity type provided in substantially the entire first mainsurface of the semiconductor chip; (c) a substantially rectangularactive cell region provided substantially at a middle portion of thefirst main surface, peripheral side regions provided outside the activecell region along individual sides of the active cell region, andperipheral corner regions provided between adjacent peripheral sideregions; (d) a first super-junction structure having a first orientationand provided in substantially the entire surface of the cell region andin the drift region; (e) second and third super-junction structures eachhaving substantially the same width and orientation as those of thefirst super-junction structure and provided in the drift region of eachof the peripheral side regions on opposite sides of the active cellregion in a direction of the first orientation of the firstsuper-junction structure so as to be coupled to the first super-junctionstructure; (f) fourth and fifth super-junction structures each having anorientation substantially orthogonal to that of the first super-junctionstructure and provided in the drift region of each of the peripheralside regions on opposite sides of the active cell region in a directionorthogonal to the first orientation of the first super-junctionstructure; (g) a main junction region of a second conductivity typewhich is at an outer end portion of the active cell region and providedin a surface of the drift region so as to surround the active cellregion; and (h) a surface resurf region of the second conductivity typeprovided in the surface of the drift region so as to be coupled to anouter end of the main junction region and surround the main junctionregion, wherein, for each of the peripheral side regions, in plan view,an outer end of the surface resurf region is located at or near a middlebetween the outer end of the main junction region and an outer end of aperipheral super-junction region formed of the second to fifthsuper-junction structures.
 2. A semiconductor device according to claim1, wherein, for each of the peripheral side regions, in the plan view,the outer end of the surface resurf region is located substantially atthe middle between the outer end of the main junction region and theouter end of the peripheral super-junction region formed of the secondto fifth super-junction structures.
 3. A semiconductor device accordingto claim 2, wherein the first to fifth super-junction structures areformed by a trench epitaxial filling method.
 4. A semiconductor deviceaccording to claim 3, wherein a plurality of floating field plates areprovided over the peripheral super-junction region formed of the secondto fifth super-junction structures so as to encircle the active region.5. A semiconductor device according to claim 4, wherein each of thefloating field plates has a rectangular frame shape in the plan view,each field plate having corner portions that are each bent at a rightangle.
 6. A semiconductor device according to claim 5, wherein each ofthe peripheral corner regions is provided with a corner-portionsuper-junction structure which is substantially line-symmetrical withrespect to a diagonal line of the semiconductor chip extending throughthe corner-portion super-junction structure so as to divide theperipheral corner region into two subregions, one of the subregions isadjacent to one of the fourth and fifth super-junction structures andhas substantially the same width and orientation as those of the fourthsuper-junction structure, and the other of the subregions is adjacent toone of the second and third super-junction structures and hassubstantially the same width and orientation as those of the secondsuper-junction structure.
 7. A semiconductor device according to claim5, wherein each of the peripheral corner regions is provided with acorner-portion super-junction structure having substantially the samewidth and orientation as those of the fourth super-junction structure.8. A semiconductor device according to claim 7, wherein, for each of theperipheral corner regions, the corner-portion super-junction structureis trimmed at an outer portion thereof such that a length of columns ofthe corner-portion super-junction varies in the direction orthogonal tothe first orientation so as to leave an outer portion of the peripheralcorner region without a super-junction structure.
 9. A semiconductordevice according to claim 4, wherein each of the floating field platesshows a rectangular frame shape in the plan view, each field platehaving corner portions that are each roundly curved.
 10. A semiconductordevice, comprising: (a) a semiconductor chip having a first main surfaceprovided with a source electrode of a power MOSFET and a second mainsurface provided with a drain electrode of the power MOSFET; (b) a driftregion of a first conductivity type provided in substantially the entirefirst main surface of the semiconductor chip; (c) a substantiallyrectangular active cell region provided substantially at a middleportion of the first main surface, peripheral side regions providedoutside the active cell region along individual sides of the active cellregion, and peripheral corner regions between adjacent peripheral sideregions; (d) a first super-junction structure having a first orientationand provided in substantially the entire surface of the cell region andin the drift region; (e) second and third super-junction structures eachhaving substantially the same width and orientation as those of thefirst super-junction structure and provided in the drift region of eachof the peripheral side regions on opposite sides of the active cellregion in a direction of the first orientation of the firstsuper-junction structure so as to be coupled to the first super-junctionstructure; (f) fourth and fifth super-junction structures each having anorientation substantially orthogonal to that of the first super-junctionstructure and provided in the drift region of each of the peripheralside regions on opposite sides of the active cell region in a directionorthogonal to the first orientation of the first super-junctionstructure; (g) a main junction region of a second conductivity typewhich is at an outer end portion of the active cell region and providedin a surface of the drift region so as to surround the active cellregion; (h) a surface resurf region of the second conductivity typeprovided in the surface of the drift region so as to be coupled to anouter end of the main junction region and surround the main junctionregion; and (i) a plurality of corner-portion super-junction structures,each corner-portion super-junction structure being provided in arespective one of the peripheral corner regions such that saidcorner-portion super-junction structure is substantiallyline-symmetrical with respect to a diagonal line of the semiconductorchip extending through the corner-portion super-junction structure so asto divide the peripheral corner region into two subregions, wherein thesubregions adjacent to one of the fourth and fifth super-junctionstructures have substantially the same width and orientation as those ofthe fourth super-junction structure, and the subregions adjacent to oneof the second and third super-junction structures have substantially thesame width and orientation as those of the second super-junctionstructure.
 11. A semiconductor device according to claim 10, wherein,for each of the peripheral side regions, in plan view, an outer end ofthe surface resurf region is located at or near a middle between theouter end of the main junction region and an outer end of a peripheralsuper-junction region formed of the second to fifth super-junctionstructures.
 12. A semiconductor device according to claim 10, wherein,for each of the peripheral side regions, in plan view, an outer end ofthe surface resurf region is located substantially at a middle betweenthe outer end of the main junction region and an outer end of aperipheral super-junction region formed of the second to fifthsuper-junction structures.
 13. A semiconductor device according to claim12, wherein the first to fifth super-junction structures are formed by atrench epitaxial filling method.
 14. A semiconductor device according toclaim 13, wherein a plurality of floating field plates are provided overthe peripheral super-junction region formed of the second to fifthsuper-junction structures so as to encircle the active region.
 15. Asemiconductor device, comprising: (a) a semiconductor chip having afirst main surface provided with a source electrode of a power MOSFETand a second main surface provided with a drain electrode of the powerMOSFET; (b) a drift region of a first conductivity type provided insubstantially the entire first main surface of the semiconductor chip;(c) a substantially rectangular active cell region providedsubstantially at a middle portion of the first main surface, peripheralside regions provided outside the active cell region along individualsides of the active cell region, and peripheral corner regions providedbetween adjacent peripheral side regions; (d) a first super-junctionstructure having a first orientation and provided in substantially theentire surface of the cell region and in the drift region; (e) secondand third super-junction structures each having substantially the samewidth and orientation as those of the first super-junction structure andprovided in the drift region of each of the peripheral side regions onopposite sides of the active cell region in a direction of the firstorientation of the first super-junction structure so as to be coupled tothe first super-junction structure; (f) fourth and fifth super-junctionstructures each having an orientation substantially orthogonal to thatof the first super-junction structure and provided in the drift regionof each of the peripheral side regions on opposite sides of the activecell region in a direction orthogonal to the first orientation of thefirst super-junction structure; (g) a main junction region of a secondconductivity type which is at an outer end portion of the active cellregion and provided in a surface of the drift region so as to surroundthe active cell region; (h) a surface resurf region of the secondconductivity type provided in the surface of the drift region so as tobe coupled to an outer end of the main junction region and surround themain junction region; and (i) a corner-portion super-junction structureprovided in each of the peripheral corner regions, having substantiallythe same width and orientation as those of the fourth super-junctionstructure, wherein each corner-portion super-junction structure istrimmed at an outer portion thereof such that a length of columns of thecorner-portion super-junction varies in the direction orthogonal to thefirst orientation so as to leave an outer portion of each peripheralcorner region without a super-junction structure.
 16. A semiconductordevice according to claim 15, wherein, for each of the peripheral sideregions, in plan view, an outer end of the surface resurf region islocated at or near a middle between the outer end of the main junctionregion and an outer end of a peripheral super-junction region formed ofthe second to fifth super-junction structures.
 17. A semiconductordevice according to claim 15, wherein, for each of the peripheral sideregions, in plan view, an outer end of the surface resurf region islocated substantially at a middle between the outer end of the mainjunction region and an outer end of a peripheral super-junction regionformed of the second to fifth super-junction structures.
 18. Asemiconductor device according to claim 17, wherein the first to fifthsuper-junction structures are formed by a trench epitaxial fillingmethod.
 19. A semiconductor device according to claim 18, wherein aplurality of floating field plates are provided over the peripheralsuper-junction region formed of the second to fifth super-junctionstructures so as to encircle the active region.